GRAPES is an acronym of the list of topics to avoid at Thanksgiving (or any holiday or celebration in which you must share space with relatives):
Guns, Religion, Abortion, Politics, Economics, Sexuality.
Don't talk about GRAPES, you'll set off Uncle So-and-So's conspiracy spiral. Again.
Cousin 1: So what do you think about the new church they're buil-
Cousin 2: SHHH, we don't go near GRAPES when the entire family has to share a house for hours and hours.
Occasional slang for testicles. I can't believe I don't see this definition here yet. There are so many terms for a guy's nuts, and this is just another. If someone refers to a guy's grapes, you know what they mean.
"He has to have huge grapes to have even attempted that stunt.