(Noun) Friends that aren't so well endowed/have small breasts, relatively female.
I'm just hanging out with my flat mates
1. A femail friend with small or non-existant mammaries
2. A person who lives in the same flat as you.
What do you think of Emma?
I'm going for a beer with my flatmates.
A person with whom one shares a rental property.
AKA a room mate
Someone to split the rent with. (If they have the money)
Tom: Whoa, Somebody broke in and trashed your apartment while you were gone!
You: I wish. No, it was just my Flat mate, he's a pig.
You: Hey will you wash the dishes?
Flat mate: Ignores you and goes to his room.
I girl from Australia or New Zealand chick that is flat chested slut who you have sex with..
A Flatmate is; A flat chested girl from the the south pacific, generalized towards Kiwis and Aussies chick, whom were not "blessed" with tits!