rub one out

From the act of rubbing a "nut" (a seminal ejaculate) out of one's penis.

rub one out (third-person singular simple present rubs one out, present participle rubbing one out, simple past and past participle rubbed one out)

1. (sexuality, slang, vulgar, of a man) To masturbate to the point of ejaculation
   • 2012, David Wambaugh, The Last Call, page 178:

     Irish sounded serious when he said, “Oh, yeah, dog, if you get caught rubbing one out in the joint, you're fucked.” I said, “What's rubbing one out mean?” He cackled, and said, “Whackin' off, chokin' your chicken, spankin' the monkey. Come on dog, don't play stupid.”

• jack off
• jerk off