The frightening moaning creature that two people become when they engage in intercourse
Watch a porno and you'll know what I mean. The beast with two backs can even be found in your bedroom or any popular sexual habitat
by Marisha A January 20, 2007
A man and woman engaged in an act of sexual intercourse. An expression whose usage dates at least as early 1604, being mentioned in Shakespeare's Othello.
Your girlfriend and your bestfriend are making the beast with two backs.
by Lenee January 14, 2007