basically a combination of smash and bang as a verb, to describe sex or the motion of sex. From my knowlege it came from a song "Lemme Smang it" by Yung Humma ft Flynt Flossy of Turquoise Jeep Records. The song is on youtube and Itunes. There is a specific dance which is also associated with word, as seen in the video.
that girl is fine, I just want to smang it to the moon.
To "Smash" and "Bang" during a sexual encounter. This is a particular maneuver used during the act of sex when the man doing the "Smanging" is unable to provide full satisfaction to their female partner during the course of his normal sexual routine. Normally causes a permanent bowing of the legs and a partially permanent vision impairment if done correctly.
The first time we made love she did not feel much and I cried so this time I will have to Smang her.