A love smack is a sharp smack on the rear of a man or woman during intercourse. Usually, it is initiated through vigorous copulation and or vocal stimulation.
A love smack can be used with an open hand, a belt, a fire-poker, or a ping pong paddle. The harder, usually, the more it stimulates the hitter/hittee.
"This guy love smacked me so hard last night that my butt looks like the cheeks of a chubby blushing dwarf"
"Yeah dude. I love smacked the crap out of this chick with dreads yesterday. It was so hard her ass almost caved in."