Cactus Effect 

The cactus effect is the feeling when you've newly shaved your balls and your sack stings your penis.

"Man, I've got a really bad cactus effect now."
"You've shaved your balls wrong!"

Cactus Effect by D-bed December 18, 2011

The cactus effect 

Term to refer to a mans balls after recently being shaved, when the small prickly hairs begin to grow back and poke his penis as it hangs over them.

Guy: Damn, I got the cactus effect. Should've shaved better.
Guy 2: I know, that shit sucks. Feels like tiny needles stabbing your dick.

The cactus effect by PurplePagan June 7, 2007