When your ass is really hairy and you sometimes get random shit (no pun intended) whether its actual shit, or underwear lint, stuck in said ass hair. Then you find it and it looks like a little gnocci and you pull it out and grunt. Hence the name grunt berry. The berry is usually fibrous and full of protein if you have a dog or cat they will most likely eat it.
"Dude I just pulled out a grunt berry the size of a fucking golf ball." "Here doggy, who likes the skippy peanutbutter??! Eat my grunt berry bitch!"
by Santiago Arroba March 16, 2008