The manky stuff that builds up on keyboard letters and in the keyboard over a period of time, especially in schools/colleges where 200 odd dirty fingered teens use them each day.
Teen 1: Dude, look at this keyboard cheesizzle, bitchin
Teen 2: Man, thats ill, no diggity?
the icky black material that always gets stuck on my mouse
what's 'keyboard cheese' made of anyway?