An acronym for "massive mammary syndrome."
When a girl has very large boobs, making it difficult for males to keep their eyes above a female's neck. one very prominent symptom of massive mammary syndrome is the significant number of "cat calls" one might receive on a daily basis.
Also used as an excuse for why clothing never fits busty chicks correctly. The cause of bathing suit/bra frustration, and accidental flashing.
-"did that creepy man just honk at you?"
-"yahh, that's typical... i suffer from MMS"
-"yo, you're left boob is hanging out of your bikini top, and you have a significant amount of under-boob going on..."
-"oh, that's just a symptom of my "MMS." don't worry about it.