When an American is so hot that you just want to tackle them and have sex with them on the spot.
As most natural-born Americans are fat, lazy, greasy, and smelly, the term "PHAT American" usually refers to a (typically illegal) immigrant. In addition to immigrants being more sexy, it is a well-known fact that illegal immigrants are much easier rape targets as they can't go to the police.
Person 1: hey mate, look at her
Person 2: oi she's got a phat Chad
Naturally large breasts, usually so large as to not be self supporting.
You've got to love a MILF with phat whaps!
A player who camps ( stays in one spot ) or sets trip wires while playing Call of Duty or various other multiplayer games.
Guy: That guy must be dead, he hasn't moved in 30 minutes
Guy 2: Nah, he just has a case of Phat Jackson