I was watching "Analyse This!" film and noticed that those mobsters used the word "to wack" a lot. I guessed it means "to kill", for example, Vitti's father was wacked in a restaurant or somebody wacked someone else. I wonder, is it usual argot word only among "Italian" mafiosi, or is it all-American slang, or in any English-speaking country? What else you may say with this "wack" word?