no mames guey means: Mexicans use this Spanish slang expression a lot. Geuy is a Spanish slang phrase that means “a jerk”. Other translations of guey include dude, bro and punk. However, young Mexicans use the term to address their friends in a playful way. Although “no mames” literally means “You must have been kidding man”, most people refer to it as “Don’t fuck me” or “Don’t give me shit”. (in Community Dictionary, added by Sherlyn Drake)