n A machine or other device designed to catch (and sometimes kill) animals, either by holding them in a container, or by catching hold of part of the body.
n A trick or arrangement designed to catch someone in a more general sense.
n A wooden instrument shaped somewhat like a shoe, used in the game of trapball; the game of trapball itself.
n Any device used to hold and suddenly release an object.
n A bend, sag, or other device in a waste-pipe arranged so that the liquid contents form a seal which prevents the escape of noxious gases, but permits the flow of liquids.
n A place in a water pipe, pump, etc., where air accumulates for want of an outlet.
n (historical) A light two-wheeled carriage with springs.
n (rfv-sense|section=trap - stepladder) A kind of movable stepladder.