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.
What up Smackback? Look at this mutha***** smackback lol