penis wobble
When you're about to nutt but then your dick shrinks down to the Donald-Trump-sized nub of a cock that it originally was and it's so wobbly that you can't enjoy it and your partner becomes very pissy with you.
Garry: "Oh for fuck's sake! I've got that penis wobble again!"
Marry: "Goddammit! It was just getting good! Quick! Go get the Viagra!"
Marry: "Goddammit! It was just getting good! Quick! Go get the Viagra!"