A stereotypeism is a phrase usually said on TV by an actor playing a foreign/reigional character and completely screwing up by resorting to stereotypes. Nearly always seen when an american tries to play an English person, who they always say are British DESPITE the fact that britain includes Wales and Scotland as well, and they're either posh or a cockney despite the fact that there are hundreds of dialects to choose from. Stupid yanks.
It's all Hugh Grant's fault actually.
Note: we english actors are much better at putting on american accents, like Hugh Lauire in House. And we're better actors anyway which is why we always play the bad guys.
Yank actor:"Tally ho, what? I'm British you know! Mm toodle pip, must go and polish my statue of the queen, what what?"
English person watching telly: "What a dipstick, using a typical stereotypeism like that."
American watching same TV: "Yeah man he got that Brit accent right on! GO AMERICA! WHO WANTS BEER AND CHIPS? HELL YEAH!"
*fight propmtley ensues*