The point during sexual intercourse where a man is irreversibly about to blow his load. The very worst time to have to cease coitus in an emergency.

Voluntarily Celibate.
A person who chooses to be celibate. Can be for any given amount of time, for a short period or for their entire life. Can be for religious reasons or not.

related: incel

The facial expression during sex that coincides with the last thrust before coming.
Imagine the contorted 'fuck face' being pulled by the male as hes about to come, and compare to the wincing one would experience when sucking a lemon, or tasting vinegar. Hence, the vinegar stroke.

the pre-orgasmal point of no return for men during the sexual act, where failing to blurt your mess will result in blue balls

The final moments prior to when a man orgasms. At this point he can no longer stop himself from ejaculating no matter what happens. He will make a face as though he has just smelled vinegar. It is said that if you peer into a man's eyes during his vinegar strokes you get a glimpse of his soul.

The often odd, varied and bizarre facial expressions a man make at the point when he is is just about to ejaculate. The same sort of faces you would pull if you had just quaffed a pint of vinegar.

the point of no return for a man during sexual intercourse in which he can not stop until he ejaculates, and looks as if someone put a spoon full of vinegar and made him smell it

as seen on "the league"