Noun- A human homosexual male's anus that is frequently penetrated and enjoyed by another gay man's penis. In male homosexual couples, the anus of the "receiver."
"Franz have you been cheating, your dick smells like another man's buttpussy?"
or
"That guy is so flamboyantly gay, you know he has a really loose buttpussy."
ButtCussion: Severe fall landing directly on one's posterior axis, causing severe pain to the point of nausea - as in a "concussion of the butt." Falling and landing directly on the gluteus maximus or worse, a direct blow to the coccyx, with pain so severe that it causes concussion-like symptoms.
He jumped up into the air over the frozen swimming pool, cannonball-style with ass pointed down and knees up, thinking the ice would break and he would polar bear it but the ice did not break - Total Buttcussion!!