Person 1: Hey, I wanted to talk to you about last night...
Person 2: Hey, you know what? BIYM! Okay? Last night never happened.
by K Wheezle May 26, 2004
Get the BIYM mug.
BIYM stands for Balls. In. Your. Mouth. Its the perfect comeback and is always fun to use and say with your friends or even your parents.
"deez nuts in your mouth hahahaha"
"boy BIYM"
"what..."
"BALLS IN YOUR MOUTH HAHAHAH"
by asherinalol February 18, 2022
Get the BIYM mug.
“My newest Tinder hookup frequently verified with me that he wasn’t crossing any boundaries, and I was all for it; until, he mentioned biym. Not a fan.”

Or

Did the biym trick work with your boyfriend?
by Ibeliveinjustice January 9, 2020
Get the biym mug.