This is a word used for people who act, dress, talk like people they aren't. It's a label for a person who is pretending they are someone totally different. It's most often used to describe people calling themsevles "punk."
Lil Johnny Bob is such a f*cking poser. He gets liberty spikes and puts safety pins in everything he owns and now automatically assumes he's a punk rocker child?! Bullsh*t!
I'm not talking about the supermarket brand labels but instead the every day, more common one. It's given to kids based on their appearance, music they listen to and how they talk. The most common labels today are: prep, gothic, punk, emo, jock, etc. Now in days, kids are label themselves because it makes them feel "cool." You find it a lot in AIM screenames like EmoKid, PunkBaby, PreppySlut.
Dude, I'd label you as a prep for sure!