They are usually 20+ and also fluent in poetry and 'the arts', and are the first to stereotype you, or anyone, and use this against them for the remainder of the said person's life.
In general; extremely obnoxious people whom are indescribably arrogant yet impossible to get through to due to the thick layer of love for themselves they have through their 'sophisticated' yet ironically simple minded taste in music and art.
The term's origin is unknown but it has been seen popping up in lyrics for various works of music across the musical scene;
A good example being in a work by John Zorn (avant garde music) whom composed a song called 'Eat Shit Jazz Snob". The Jazz influence in his music supported the hatred of such people and the level of hypocrisy they carry with them.
Jon: "Hi" *Pulls out earphones*
Jonathan: "What was that you are listening to, some horrible uninspired heavy metal music" *Sigh*
Jon: "Some unreleased compositions by Max Ritcher actually you JAZZ SNOB!"