a lewdly obscure reference to a woman being good looking. Mint = perfect, box = pussy. "that's some good lookin' pussy!" It's literal meaning is supposed to be akin to "she's hot", or "that's one great looking woman"
by emefbe December 12, 2016

Girl: Did you see that new shirt Pete bought?
Friend: It's not gonna help, Pete's mint in the box ugly
Friend: It's not gonna help, Pete's mint in the box ugly
by poofu's gal September 25, 2007
