Originated from, and first performed by rap artist M.K.Russ., the action of a "M.K. Pump" occurs during, or shortly after a 'ballin' or 'pimp juice' action. It is meant to both taunt the opposition or audience such action is being performed upon, as well as to further increase your status as a 'balla', or a 'pimp juice' playa.
Mathias: Shiiiit, I saw you put his ass on the ground with that move!
Detox: Hell yea, that was sick man! And ofcourse you had to follow it up with the M.K. Pump!