Slightly old-fashioned term for what is usually today called a "Billy Club" or (UK) an officer's baton, a rodlike piece of wood, usually painted black, worn by police to strike or subdue suspects.
In the USA many registered, private security guards who are not licensed to carry firearms may carry a Night Stick.
Certain phallic implications are almost inevitable.
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In the 1940s, practically every American beat patrolman was equipped with a .38 revolver and a black NightStick.
You are getting a blow job and then your buddy that was hiding around the corner with a bonner sneaks up and whacks her in the head with his cock
On my wedding night I was getting a blow job and out of nowhere my brother came around the corner with his wang out and smacked a bitch in the face and ko'd her ass. "Night stick Biotch"
Getting a blowjob, as your friend comes around the corner with his dick, and smacks her across the head inconspicously.
Jamie was getting head from a girl, when his buddyDale was lurking around the corner, suddenly she gets hit with his pecker in the head. she was night sticked