doppelbänging 

Having sex with yourself through the creative use of a time-machine.

Twilight is so gay that in order to be gayer, you'd have to be discovered with a time machine, doppelbänging yourself.

doppelbänging by Seapoo June 9, 2010

Dopplebanging 

The act of hatefucking a person for no reason other than that said person bears a passing resemblance to your ex.

"I got so drunk last night, I wound up dopplebanging a Starbucks barista against a vending machine"

"I'm so sorry I dopplebanged your mom"

"Paul just got dopplebanged"

Dopplebanging by Amiahipstermaybe December 5, 2011