adj. - a woman that in no conceivable way would have sex with the other parties at hand. Out of his league, untouchable or "only in your dreams". Only used when no one present has any realistic and/or legal means of penetrating the pussy of the subject, direct object or indirect object which the adjective refers to. (In a grammatical sense; this does not imply that women are subjects or objects.) May also refer to a hook up that no one believes and is totally unverifiable.
Other spellings: impussable, impussible, im-fucking-pussyble.
A term used to describe a version of the female species who is in no conceivable way willing to interact in sexual activity. No matter how hard you try, she will not give it up.
1.) "Dude! I'm totally gonna hook up with that Tammy chick tonight!"
"No way man, she's a virgin Mormon. There is no way you're getting past that force field. That's mission: impussable."
2.) "Man, i totally thought i was going to score with this drunk chick last night, but she would not put out. She was being so impussable."