Usually an exclamation that indicates that something is extreme such as surprise, wonder or anger. Also any other emotion, thought or action that is thought to be extreme.
Mike was so high one time when he was smoking some weed he said "Hit Yo! That's some good weed!"
Someone of low intelligence who believes they must lick the window in order to clean it.
Mike's ex wife Jill is such a window licker she lost her job at Walmart and got hired as a window washer at IBM. She then proceeded to lick the windows in order to clean them. When her boss caught her doing this she was fired from IBM as well. Jill is a big fat window licker.