posh twat
Basically, and with some variations..
A posh twat is an incredibly blonde girl, who, though dislike by most, thinks everyone wants to be them. Don't be fooled though, their only friends are each other. Role models include The Plastics and Paris Hilton. Posh Twats exhibit behavior such as pretending to be bisexual so people pay attention to them, continually repeating how they "dont care" what you think of them, and taking myspace pictures with weird pouty expressions. 
Posh Twat: OMG STOP STARING AT MEEEEEEEEEEE
Kid 1: ...I was looking at my girlfriend behind you.
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Posh Twat: And like, I was so upset, because like the car they wanted to buy me was like, purple instead of like, white. I need my girlfriend to come make me feel better. :(