A specimen that is prone to be of high levels of irritance to the normal person. In general, they hold the belief that their musical taste and their musical taste alone is relevant while anyone who has opposing or different opinions on music is considered stupid and won't hesitate to spew snotty remarks at you. These people are often pretentious poseurs who always make an ass out of themselves as they claim to be "non-conformist" for listening to indie bands with quirky names who have song titles that are at least ten words in length. The funny thing is, is that they don't realize that they are actually the biggest conformers out there for listening to, or claiming to listen to certain bands or genres in order to fit into a certain scene or gain some cred.
Generalizations aside, they are the Adolf Hitlers of music and if you don't like the exact same music they do, they will cut you down in ridiculous ways for having a different opinion and it often leads to broken friendships. If you find that you are friends with a music snob, do yourselves a favor and just cut them loose right away. It'll save your fist from being hit by their face when they find out you listen to mainstream. There are some who will even criticize others for not being as pedantic about music or a band as they are or even simple things as to why you are interested in the artists you like.
General music snob: Excuse me? You listen to Britney Spears? That's not real music; that's manufactured crap! Try listening to real music like Suzie Crotchrocket and the Breast Rashes!
Pretentious poseur: All the bands I listen to are known by fewer than 100 people and you can't find their albums in stores, so that totally means I have a better taste in music than everyone! I'm so HxC!
Know-it-all: Unless you read the liner notes of every album, read all of their biographies, know all the words to their released and unreleased songs by heart AND look up every possible bit of information on the band as soon as you hear about them on the internet like I do, you don't deserve to call yourself a fan of music! Hmph!