Commonly used to describe a
girl with the tits of a 10 year old annorexic
male. Can be referenced to as an acronym, meaning "Forever Lacking Any
Titties".
Person
1: I gotta say, Emma's pretty
hot, I think I'll go for it
Person 2: Are you joking?? She's as flat as the Great Plains!
Alternatively, with the acronym in place...
Person
1: I gotta say, Emma's pretty
hot, I think I'll go for it
Person 2: Are you kidding me? She is, and will forever, be F.L.A.T
(The first instance is much more commonly used)