Terms starting with M

The beam quality factor: how many times worse a beam focuses and diverges than an ideal Gaussian of the same wavelength.

The principal lunar semidiurnal constituent, period 12.42 hours, usually the largest part of the tide.

A small oval around a target color on a chromaticity chart, inside which color shifts go unnoticed by most viewers.

The thick reference book every machinist owns, covering threads, fits, materials, speeds and formulas.

A bend in a fiber tight enough to see, which lets light escape the core and causes loss.

Clipped shop word for magnesia, magnesia brick or a magnesia-based mix. Shop talk

Field name for a magnesium sacrificial anode, the high-voltage choice for high-resistivity soils. Shop talk

Magnetic drain plug that collects ferrous wear debris and is checked at oil changes as a quick wear gauge. Shop talk

Joking name for the smoke a burnt-out component releases, as if the smoke were what made it work. Shop talk

Joke that electrical parts run on smoke sealed inside them, because once it gets out they stop working. Shop talk

Resin-bonded brick of magnesia and graphite, the workhorse lining of BOFs, electric arc furnaces and ladle slag lines.

Basic brick of magnesia and chrome ore, prized for resistance to aggressive slags in copper smelting and degassers.

Checking steel with a magnet while heating, since it stops being magnetic near its hardening temperature. Shop talk

The principal track or tracks of a railroad between terminals, where trains need authority to run.

A large-capacity air vent at the end of a steam main that lets air out fast so steam can fill the main.

The primary set of parallel survey lines that delivers the required depth coverage over a survey area.

The largest diameter of a screw thread, over the crests of an external thread or the roots of an internal one.

To splice, pigtail and fold the wires in a box so it is ready for a device or cover. Shop talk

To screw a threaded joint together and tighten it, or to assemble and torque a flanged joint. Shop talk

Fresh water added to a boiler system to replace water lost to leaks, blowdown, venting and unreturned condensate.

Said of a tide that is rising, or of the fortnightly cycle building from neaps toward springs. Shop talk

Shop phrase for machines actually cutting metal, the productive part of the day as opposed to setup. Shop talk

Multimode test jumper wound around a smooth rod to strip out high-order modes and stabilize loss readings.

A freight train carrying a mix of car types and commodities for many different customers.

Swirls and streaks of separate colors in a two-part adhesive that show it has not mixed thoroughly. Shop talk

The spare optical power left after link loss is subtracted from what the transmitter and receiver can tolerate.

Quenching steel into hot oil or salt just above Ms, holding to even out temperature, then air cooling.

The hard, needle-like phase that forms when austenite is quenched fast enough to trap its carbon.

Minimum average roll value: the lowest average test result a product guarantees for any roll it ships.

Protecting threads, holes and contact surfaces from powder with heat-resistant tape, caps and plugs.

Covering areas of a part that must not be blasted or coated, using tapes, plugs, shields or maskants.

Weight of a geosynthetic per square meter or square yard, the basic identity check for geotextiles.

The freshly laid strip of asphalt behind the paver, before and during rolling.

Estimating in-place concrete strength from its temperature history, recorded by sensors cast into the pour.

Maximum allowable working pressure: the highest pressure a boiler is approved to operate at, stamped on its nameplate.

The peak strength of the flood current in a cycle, and the time it occurs; max ebb is the seaward equivalent. Shop talk

Multibeam echo sounder: a sonar that measures a fan of depths across the track on every ping, covering a wide swath.

Thousands of Btu per hour: the everyday unit for rating heating boilers, burners and heating loads.

Metal-clad cable: insulated conductors, including a green ground, inside interlocked aluminium or steel armor.

Family of oxidation-resistant alloys of nickel or cobalt with chromium, aluminum and yttrium.

Machine direction: the direction a nonwoven travels through the line, along the length of the roll.

Average distance a gas molecule travels before it collides with another molecule.

White spots or crosses inside a laminate where glass fibers have parted from the resin at weave crossings.

The exact quantity a measurement is aimed at, pinned down tightly enough that everyone measures the same thing.

The equation linking the output quantity you report to all the input quantities that feed into it.

Measuring across precision pins or balls placed in opposite tooth spaces to check tooth thickness.

The reported value of a measurand together with its uncertainty, the full answer rather than just a number.

Lab slang for the oil-sealed rotary vane pump that sits under the bench or behind the tool. Shop talk

Adhesion gained by adhesive flowing into pores and roughness and locking in once it hardens.

A joint that holds two cleaved fiber ends together in an alignment device with index-matching gel, no arc needed.

The band between about 1 and 10⁻³ mbar, where gas flow shifts from fluid-like to molecule-by-molecule.

Insulation resistance tester, and the verb for testing a cable or motor with one. Shop talk

To test insulation resistance with a high-voltage DC tester; also the jobsite name for the tester itself. Shop talk

A cure check that rubs the film with a cloth soaked in methyl ethyl ketone and rates how much softens or rubs off.

Melanopic Equivalent Daylight Illuminance: a measure, in lux, of how strongly light stimulates the eye's circadian system.

Grams of molten polymer pushed through a standard die in 10 minutes, the basic measure of how easily a resin flows.

Web of very fine fibers made by blasting molten polymer from a row of tiny die holes with hot, high-speed air.

Minimum efficiency reporting value: a 1 to 16 rating of how well an air filter captures particles of different sizes.

The engagement of two gears' teeth, or the zone where they meet; also the verb for gears engaging.

A continuous furnace that carries parts on a wire mesh belt through heating, quench and wash in one line.

Describes the in-between vision of twilight and street lighting, when rods and cones both contribute.

Shop and field name for thermal spraying, especially zinc and aluminum sprayed on steel for corrosion. Shop talk

The effect where two colors match under one light source but not under another, because their spectra differ.

Two samples matching in color under one light but not under another, because their reflectance curves differ.

Meter socket enclosure where the utility revenue meter plugs in, mounted between the service drop and panel. Shop talk

Dispensing equipment that pumps two adhesive components from bulk containers in a set ratio and mixes them on demand.

The restriction that drops refrigerant from high side to low side pressure and controls how much enters the evaporator.

Mean Higher High Water: the average height of the higher of each day's two high waters over the datum epoch.

Mean High Water: the mean height of every high tide across the datum epoch, often the line that defines the legal shoreline.

Microbiologically influenced corrosion: corrosion started or sped up by bacteria and other microbes.

Short for micrometer, pronounced mike, and the verb for measuring a part with one. Shop talk

A tiny, invisible deformation of the fiber axis caused by pressure, which scatters light out of the core.

Hardness measured with very small loads under a microscope, used for thin cases and individual phases.

Hardness of a coating measured with tiny diamond indents on a polished cross section.

Shop name for a millitorr, one thousandth of a Torr, used in US furnace shops, labs and refrigeration work. Shop talk

An electronic vacuum gauge that reads very low absolute pressure in microns of mercury during evacuation.

Very fine surface fatigue pits, too small to see one by one, that give tooth flanks a dull gray look.

Fatigue damage made of tiny pits, about 10 to 20 microns deep, that turns gear and bearing surfaces dull gray.

Very small laser-drilled via, typically 0.15 mm or less across, spanning one thin dielectric layer.

A non-contact water level sensor mounted above the surface that measures the distance down to the water by radar.

One thousandth of an inch, the unit North American crews use for geomembrane thickness.

One thousandth of an inch, exactly 25.4 microns, the everyday unit for coating thickness in North America.

One thousandth of an inch (25.4 micrometers), the usual North American unit for coating thickness.

Oil turned milky or creamy by emulsified water, seen in gearboxes, hydraulics and engines. Shop talk

Pump oil turned cloudy or creamy by an emulsion of water, a sign the pump has been swallowing wet loads. Shop talk

A resurfacing job where the old surface is milled off and repaved with new mix, often the same day. Shop talk

Shop name for the material test report tracing steel back to its mill heat, chemistry and test results. Shop talk

Blue-black iron oxide skin formed on steel during hot rolling, which must come off before painting.

One thousandth of a bar, equal to 100 Pa, and the default pressure unit in European vacuum work.

Grinding off the top of an existing pavement with a rotating cutter drum before repaving.

Steel conduit hanger with a bolt across the top, used to hang pipe from rod or fasten it to strut or steel. Shop talk

A ductless split system with an outdoor inverter unit connected to one or more indoor heads by refrigerant lines.

The smallest diameter of a screw thread, at the roots of an external thread or the crests of an internal one.

A magenta correction gel that removes the green tint from fluorescent or green-shifted LED light for camera work. Shop talk

A low tide predicted to fall below the chart datum zero, shown as a negative number in the tide table. Shop talk

The recipe for a concrete mix: the weights of cement, SCMs, water, aggregates and admixtures per cubic yard.

The proportion of resin to hardener in a two-part adhesive, given by volume or by weight.

Transitional regime where the load is shared between a partial fluid film and asperity contact.

A tide with two highs and two lows a day of clearly unequal heights, combining semidiurnal and diurnal parts.

Mean Lower Low Water: the average height of the lower of each day's two low waters, used as chart datum in the United States.

Main lugs only: a panel with no main breaker, fed through lugs from a breaker or fuse somewhere upstream.

Methyl methacrylate, the monomer behind most structural acrylic adhesives and the shorthand name for them.

Mixed metal oxide anode: titanium coated with precious-metal oxides, the standard long-life ICCP anode.

A full-size sample of a wall, window or joint assembly built and tested before the real work starts.

The modulating motor that drives a burner's air damper and fuel valve through their range on command. Shop talk

The effective width of the light spot traveling in a singlemode fiber, slightly larger than the physical core.

A sudden jump of a laser's output frequency from one cavity mode to a neighboring one.

Fixing the phases of many longitudinal modes so they add up into a train of ultrashort pulses.

The material in a reactor core that slows fast fission neutrons so they are more likely to cause further fission.

Varying a burner's firing rate continuously between low fire and high fire to match the load.

The metric measure of gear tooth size: pitch diameter in millimeters divided by the number of teeth.

Block of folded or stacked fiber blanket, compressed and fitted with anchor hardware for fast furnace lining.

How stiff a cured sealant is, meaning how much force it pulls on its bond faces when stretched.

A cure triggered by humidity in the air or on the parts, used by silicones, urethanes and silane polymers.

Flow regime in which molecules bounce between the walls almost without meeting each other.

Shop name for sprayed molybdenum, a scuff-resistant coating for piston rings, synchro rings and bond coats. Shop talk

Shop name for molybdenum disulfide, the black solid lubricant, or for any grease that contains it. Shop talk

Woven geotextile of round single-strand yarns that leaves regular open pores for high flow and good filtration.

Unshaped refractory supplied as a mix and installed in place to form a jointless lining.

Propagating uncertainty by random sampling of input distributions through the measurement model, many thousands of times.

Master Oscillator Power Amplifier: a low-power seed laser followed by amplifier stages that bring it to full power.

Mortar that falls into a masonry cavity during laying and piles up on the flashing, blocking drainage. Shop talk

Full-width roll wound at the end of the production line, before it is slit into customer rolls. Shop talk

Uneven, blotchy appearance in a print or coating, seen as cloudy patches of density or gloss.

A polished cross section of a coated coupon set in resin, used to check structure under the microscope. Shop talk

Rows of small drilled holes across breakaway tabs so boards snap cleanly from a panel, leaving a nibbled edge. Shop talk

Motor-operated valve: a valve driven by an electric actuator with a motor, gearbox, torque switch and limit switches.

How far a sealant can stretch and compress, as a percentage of joint width, while keeping its seal.

An automated moving-head light that pans, tilts and changes color, beam and gobo under remote control. Shop talk

Maintenance of way: the department and crews that build and maintain track, bridges and roadbed.

Running long parallel survey lines back and forth across an area, like cutting grass in strips. Shop talk

Milepost: the numbered marker that fixes every location on a railroad by distance along the line.

Membrane patch colorimetry, a test that measures varnish-forming material in turbine and hydraulic oils.

Maximum permissible error: the error limit an instrument must stay inside to conform, set by its spec, a standard or the law.

Multi-fiber Push-On: a single connector that terminates 8, 12, 16 or 24 fibers in one rectangular ferrule.

Mils per year, the US corrosion rate unit: thousandths of an inch of metal lost per year.

Motion reference unit: the sensor that measures a vessel's roll, pitch and heave to correct sonar data.

A silane-modified polymer that moisture-cures into a flexible, paintable, isocyanate-free adhesive-sealant.

The temperature at which martensite starts to form as austenite cools during a quench.

Measurement systems analysis: the set of studies that prove a gauge is fit for the decisions its data will drive.

Multiple stress creep recovery: a high-temperature binder test measuring how much of a deformation the binder recovers.

Mechanically stabilized earth wall: compacted fill reinforced with layers of geogrid or steel strips behind a facing.

Mean Sea Level: the plain average of a station's hourly water levels across the tidal datum epoch.

Magnetic particle testing: finding surface and near-surface cracks in steel with a magnetic field and iron powder.

Mean time between failures: average operating time between successive failures of a repairable system.

Mean Tide Level: the height midway between the mean high water and mean low water datums.

Mean time to failure: expected life of a non-repairable item, the average time until its first and only failure.

Material transfer vehicle: a machine between the trucks and the paver that remixes hot mix and feeds it nonstop.

Jobsite slang for fresh concrete, used by finishers, pumpers and ready-mix drivers alike. Shop talk

Duct mastic, the thick paste brushed over duct joints and seams to seal them airtight. Shop talk

Shop word for the clay used to plug a blast furnace taphole, and bricklayers' word for mortar. Shop talk

Network of cracks like dried mud in a coating applied too thick, typical of inorganic zinc and waterborne paints.

A network of surface cracks that looks like dried mud, from tensile stress in a coating.

Raised cover that screws onto a square box and gives a flush opening for devices in drywall or plaster. Shop talk

Bulge of very soft soil shoved up ahead of fill being placed on weak ground. Shop talk

Flat woven polyester pulling tape printed with footage marks, used for long pulls and to measure runs. Shop talk

Flat, low-stretch polyester pull tape with printed footage marks, left in conduit to pull cable later. Shop talk

Fiber with a 50 or 62.5 µm core that carries many light paths at once, used for short links inside buildings and data centers.

Multiwire branch circuit: two or three hot conductors on different phases sharing one neutral.