german word, means "headshot".
When two friends (better: a man and his girl) share a joint or blunt. Wait till the doobie gets short enough, take a deep hit, then put it your mouth backwards and blow. Your friend just opens his mouth and inhales.
Hermann: "Aaaaoooowwwww!"
Hans: "what`s wrong?"
Hermann: "the ashes just burned my tongue!"
Hans: "haha, fool. U need to be a pro smoker to do "Kopfschuss" properly!