A form, being or presence that can be blamed when u do not wish to take the consequence of your actions.
(Hershy hits Borrish in the face.)
Borrish: Owww what the hell was that for.
Hershy: What you goin onna bout, that clearly wasnt me.
Borrish: Yeah it was, I saw you do it!
Hershy: No you didn't, it was an exterior life-form
Borrish: Oh, thats ok then :)