The Collaborative International Dictionary of English v.0.48:
nightstick \nightstick\ n. A policeman's club. Syn: truncheon, billy, billy club, billystick. [WordNet 1.5]WordNet (r) 3.0 (2006):
nightstick n 1: a short stout club used primarily by policemen [syn: truncheon, nightstick, baton, billy, billystick, billy club]