greebo
'Greebo' is commonly used as an insult by chavs or townies to offend anybody that has a disimilar dress sense to themselves. May be used with any of the prefixes 'fucking', 'dirty', or 'filthy' and if being adressed by a chav or higher than average intelligence you may even get a suffix, for example: 'cunt' 'twat' or 'bastard'. This could give any number of wonderful insults like 'filthy greebo cunt'.
Other stereotypes can be used such as emo, grunger or goth but essentially to the chav mind it is all the same.
I could define the stereotypical 'greebo', 'emo' or 'goth' but really theres no need because these are just stereotypes and if you ever find yourself called one when you wouldn't necessarily consider yourself to be in that sort of social group then it is most likely because you are wearing an item of clothing that is black or hangs loosely on your frame, or if you have hair that spans between lengths of partially covering your forehead, to entirely covering your face.
To those hollering these names at you, regardless of whether they insult you or merely make you laugh at your assailant's lack of intelligence, the content of your character does not matter, they will simply assume that because you have hair that is not kept in trim with a lawn mower and that you listen to music with lyrics that do not include the words 'dawg' 'bitch' 'G' that you must worship the devil, be miserable with your life and want to end it pretty sharpish. 
It is an unfortunate occurance. Because most 'greebos'are infact regular people with regular lives, jobs and aspirations. They are only targeted with verbal abuse because they are not wearing sports tracksuits, despite the irony that chavs do wear sportswear, they would do anything to avoid exercise. 

So to anyone receiving rude remarks and words that these people don't seem to comprehend, even if they are shouting them at you, never mind. They are just calling you an individual and ever so slightly agitated that you are not a sheep like them, stabbing people, modifying cars that are deemed unroad-worthy upon purchase and giving pre-adolecents STIs.
This is a real life example, one that i had to put up with no matter how utterly stupid it actually was. This kid has called me a greebo before, just decided to comment on my hair this time instead:

I was just heading up the stairs on my way to my art lesson, second period in the day, three boys in the year below me where walking up the stairs infront of me. One of them says "get a haircut" after a little more walking in silence i thought to myself "hmm... i could form a witty response to that" but to avoid confrontation i merely grumbled a fairly quiet "no". It seems he must have been waiting for some sort of response or had just imagined one and retaliated because it's in his nature because he said "what did you say?" in as intimidating a voice as he could muster. I just looked at him with a smile and said "I'd rather not thanks." and then it began. He stopped on the stairs and gave me the typical crap. A mention about a fight, something about me starting. I was just thinking 'you stupid little twat'. so rather than turn around and take another set of stairs i carried on walking up the stairs without saying anything to him so he leant forward and tried to push me down the stairs. Really i thought this was a little harsh just because i disagreed with his judgement that i needed to cut my hair, and that i personally didn't even know this kid. 
To cut a long story short after a little of him wrapping his tiny hands around my neck and a bit of me pushing him up the stairs i made my way to my art lesson. It was only then that i regretted having been wearing a big coat, a bag on my back and a folder in my hand, and dearly wished i could have thrown him down the stairs, followed by removing some of his more important organs and leaving him in an unattractive mess on the floor. But thats just how things go eh?