vinegar stroke

(This etymology is missing or incomplete. Please add to it, or discuss it at the Etymology scriptorium.) Uncertain.

• Perhaps from the idea that the man ejaculating may have a strained facial expression like that of somebody tasting sour vinegar.
• Perhaps from the idea that when a man masturbates his strokes become faster and shorter when reaching climax similar to shaking vinegar from a bottle.

vinegar stroke (plural vinegar strokes)

1. (slang) The fast strokes during male masturbation, just before ejaculation.