To bump into another man's testicles with one's own testicles, whether intentionally or not, when one is double-penetrating a woman with another man.
The idea of a threesome intrigues me, but the chance of knockin' nuts with another dude turns me off.
by xray233 August 10, 2007
When a man who has testicles, swings his scrotum sac from left to right in a fit of joy.
Chaz was knockin' nuts when Beyonka agreed to suck his twinkie-cream.
by Jerome June 16, 2006