Lash
Lash turns up in 2 fields: gears, mechanical. Here is what it means to the people in each one.
Lash in gears
Shop clipping of backlash, the free play between mating gear teeth, as in set the lash or check lash.
The everyday shop word for backlash, especially when setting up axles, gearboxes and machine tool drives. Mechanics measure it with a dial indicator on a tooth while rocking the gear against a held pinion, and adjust it with shims, adjusters or center distance. Lash is quoted in thousandths of an inch or hundredths of a millimeter, such as eight thou on a ring gear.
"Lash is at eight thou, right in the window, now paint it and see if the pattern agrees."
Lash in mechanical
The mechanical clearance or lost motion between moving parts.
The total amount of free movement or play between mating mechanical components before they engage and transmit force. It is often intentionally designed into gears or valve trains to allow for thermal expansion and lubrication. Excessive clearance from wear creates harsh impacts, noise, and poor precision when reversing direction.
"Check the valve lash on cylinder three, it sounds like a sewing machine."