A person who is different from others (others meaning: chavs, trendys, preps, geezers - whatever you want to call them) - 'greebo' is their word for skaters, rockers, moshers, emos, goths etc. they like some sort of rock/alternative music including emo, metal, goth, punk, etc.
they dress differently from them usually in loose/baggy trousers, hoodies and band shirts and military style clothing (e.g camoflage patterns) - or girls may wear net gloves and stripey, brightly coloured tops and accesories.
they are often pretty intelligent in one way or another and are often mistaken for trouble-makers. though they are smart enough to know that fighting wont solve anything and therefore arnt actually the ones who start things - they are provoked. when a chav (insert other names here)says something they can usually answer wittily or with the use of long words - this can often confuse stupid people. many dont actually have anything against chavs but dont like them because they make their lives a misery with their constant taunts. they like to keep themselves to themselves.
chavs often dont actually know what the word means
chav: "oi, greebo! what u fukin lookin at? eh? ya startin are ya!?"
'greebo': "oh i see, its now a crime for one to glance at another?"
chav: "oooo shes tryin to be cleva wid us!"
'greebo': "correction - i wasnt 'trying'" *walks off*