Stem
Stem turns up in 2 fields: valves, maritime. Here is what it means to the people in each one.
Stem in valves
The rod that carries motion from the handwheel, lever or actuator through the bonnet to the closure member.
In linear valves the stem rises or turns to move a gate, disc or plug; in quarter-turn valves it rotates a ball, plug or disc. It passes through the packing, so its finish and straightness decide how well the packing seals. Ball valves use blowout-proof stems inserted from inside the body so that pressure cannot eject them, and a scored or bent stem is a common reason for packing leaks.
"Stem's got a bend in it from somebody's cheater bar, that's why the packing won't stop leaking."
Stem in maritime
The main vertical timber or steel bar at the very front of a ship's bow.
The upright structural member extending upward from the forward end of the keel. It forms the leading edge of the vessel, cutting through the water and providing a solid anchor point for the hull's side planks or plates. Damage to the stem compromises the entire structural integrity of the bow.
"The collision crumpled the plating right back to the stem."