Trunnion

Part of speech: noun

Definitions

1. A cylindrical pin or axle that protrudes from the side of a cannon, machine part, or other device to serve as a pivot point for rotation or support
2. A projecting pin or shaft attached to the side of an object that acts as a fulcrum or bearing point, allowing the object to turn or be suspended
3. An axle-like projection extending from the side of a gun, engine part, or similar apparatus that enables swiveling motion or provides a mounting point

Etymology: A trunnion is one of the two short cylindrical pins projecting from either side of a cannon, on which the barrel rests and pivots in its carriage. The word comes from French "trognon", meaning "core" or "stump", and the link is physical: the pin is a stub jutting out from the body of the gun, much as the core of an apple is the hard central part left behind once the flesh is gone. The trunnions are what let a heavy gun be raised, lowered and balanced, so a small projecting stump ended up doing essential mechanical work.

Synonyms: pivot, axle, pin