When one see's something or someone so ugly that they have the complete opposite of an orgasm.
Yo, every time I see that new ugly chick, I have an ingasm.
When you reach the point of no return and flex the PC muscle, causing the semen to be blocked and possibly shoot into the bladder.
Billy woke up in the middle of a wet dream. Instinctively, he flexed his PC muscle so nothing got in his underwear. It was an ingasm.