(rail transport, derogatory) A branch line train, using light equipment

(US, rail transport, apocryphal) To fill a steam locomotive water tank manually from natural water supplies (a hypothetical process whose use has been discredited).

Unthinking, not carefully considered, (nearly) automatic, spontaneous, easily predictable.

(weightlifting) The act of lifting the barbell from the floor to a resting position across the front of the shoulders (the clean phase), pausing, and thrusting the barbell over the head to a stationary position in one movement (the jerk phase). The normal technique for both parts of this act involves propelling the barbell upwards, quickly lowering the torso, and then straightening the legs.

A sudden reflexive movement of the leg below the knee, as a reaction to a tap to the tendon just below the patella (kneecap).

(vulgar, countable, slang, US) An annoying person. / (vulgar, uncountable, US) An act of masturbation. / (film) A stunt in which the performer is suddenly pulled off a horse, etc. by means of a cable.

(dated) Used other than figuratively or idiomatically: see jerk, off. / (idiomatic, slang) To masturbate, usually a male. / (intransitive, vulgar) To do nothing; to waste time.

(US, idiomatic, dated) A person who works at a soda fountain.

Alternative spelling of jerkoff

plural of jerk-off