A common misspelling of the word "Poseur", used to define someone who pretends to be something he/she is not. This type of person generally prescribes to a particular social group, in order to be trendy or popular; but does not really believe or practice anything that particular group does.
"Hey guys. I just wanted to let you know, I've become emo over the past couple of weeks."
"Really? What bands are you listening to nowadays?"
"Miley Cyrus and The Jonas Brothers."
"Screw you Poser."
"Screw you asshole. It's spelled Poseur."