Worm
Worm turns up in 2 fields: gears, maritime. Here is what it means to the people in each one.
Worm in gears
A screw-shaped gear with one or more threads that drives a worm wheel at right angles for a large reduction.
The threaded member of a worm drive, which meshes with a worm wheel on a non-intersecting shaft at 90 degrees. Each turn of a single-start worm advances the wheel one tooth, giving reductions from about 5:1 up to 100:1 in a single stage. Motion is almost entirely sliding, so efficiency falls as the ratio rises, and low-lead worms can be self-locking, though not reliably enough to replace a brake.
"Single-start worm on the gate operator, so forty to one in one stage, and it won't back-drive unless something shakes it."
Worm in maritime
To lay small yarn or twine into the spiral grooves between the strands of a larger rope.
Worming is the first step in protecting traditional laid rigging from chafe and water intrusion. A rigger winds small stuff, like marline or spun yarn, tightly into the contlines (the spiral valleys) of a heavy rope to create a smooth, cylindrical surface. This prepares the rope for the subsequent steps of parcelling (wrapping with canvas) and serving (binding tightly with twine).
"We need to worm, parcel, and serve these new shrouds before stepping the mast."