hmmm... A Poser is someone with a completely different attitude, style, and personality trying to be something on the far other side of the spectrum.
Let's use some examples.Remember, this is just my opinion.
Jeff is a nice kid. He likes some classic rock, he's got a short hair cut, very pale, and generally nice to people. Then one day, Jeff is talking to friends, and he keeps on calling everyone Dog. Now to Jeff, Jeff is the mac daddy pimp whatever you want Jeff to think of himself. BUT, To everyone else, Jeff is fucking annoying at this point. Very very very annoying. Jeff changes nearly NOTHING about him to make him more "Gangsta" but yet, he talks like he's fixing to cap someone. I mean, this was Jeff, the nice kid from the block.Now he wants to be a Baller? Everyone is soon disgusted with Jeff's actions and call him a poser. Now Jeff is an outcast. But hey, Jeff's cool! Jeff's mom says he's cool.....