A snob who prides him/herself on being a fan of all the hip-hop you never heard of. Considers any artist not selling CD's out of a Backpack on the train a "sellout". Usually a college-aged suburban kid of any race (dreadlocks optional) who discovered his consciousness at school and dives blindly into underground hip-hop and hates all commercially sucessful styles of rap music, not realizing that the artists he worships are trying to sell records too. Peppers every conversation about rap with insults about your musical tastes, then bringing up some rapper you never heard of and saying they'lll be THE FUTURE OF HIP-HOP, THE SAVIOUR OF HIP HOP, until they sell too many records, therby deeming them "wack."
Kind of like a junior version of the "jazz purist.
Me: "Hey dog, you heard that new Jeezy?"
Backpacker: "Jeezy's corny! You need to listen to MC No Name, he's the future of hip-hop!"