The word "nina pop" usually refers to the recoil effect that happens after shooting a gun. So when people "nina pop" they are jerking their bodies like the recoil or "jerkiness" of a gun.
by Sunny Capri November 17, 2003
dance move popularized in St. Louis, similar to chickenhead; name originated from body moving like it'd been shot with a nine millimeter (nina)
by B. Chips May 13, 2005