When you are boning your smoking hot girlfriend doggie or in any kind of style from behind and she smacks her arse back onto your phallus in sync with your mighty thrusts, which in turn creates a satisfying slapping sound.
by gabeisaac December 5, 2016
A smack back is whatever you want it to be. Usually relating to someone or something that is wack, lame, weak, or ugly. Can also be used as a greeting term. Like what up nigga, dog, playa, killah, ninja, ect. Smackback is a word such as bad. Can be used for good or evil. So basically its anything u want it to be.
by Kyser Soze November 8, 2007