I never hear of it but its apparently a style of music. I found out about it cause I started listening to this guy called Tinie Tempah and on all of the youtube vids I see I'll find comments saying Grime legend or he's putting grime on the map...
I'd recommend you read the brief history of grime on this website: http://funadvice.com/r/3lr3h0vud1 It explains where it started and when it evolved into the more mainstream grime you get today. It also gives example of the more grimy tracks around. Give them a listen and you'll know what grime is soon as :)
In music it's music that goes very fast, like very, very fast. I think this might give you more information or something. http://funadvice.com/r/14qerkjf4tk Other than that I found out about it in the dictionary, it means: dirt or soot, ussually accumulated in a black layer or ingrained into a surface?
