A phrase used to ridicule someone's stupidity, "big white mint" refers to a urinal cake. Thus "don't eat the big white mint" implies that someone is stupid enough to mistake the urinal cake for a mint and eat it.
I was on a date with this really dumbass guy, and he said he had to go to the bathroom. I said, OK, don't eat the big white mint.
by purplefeltangel July 03, 2006