Definition of grebo in English:
 grebo
nounPlural grebos ˈɡriːbəʊ
British informal A youth favouring heavy metal or punk rock music, and having long hair.
 Example sentencesExamples
-  It was the birthplace of the unlamented, long-haired ‘grebo ‘scene of the late 80s, whose bands sported long hair and baggy shorts onstage.
 -  But basically kids are really keen to label each other, they even told me I was a grebo because I like the Kaiser Chiefs.
 
Origin
  
1980s: perhaps from greaser, on the pattern of words such as dumbo.