Whille engaging in sexual activity one or both of the participants are fat,and their belly begins to jiggle/wiggle/slosh(sloshin') around;like waves crashing on the shore.
The sexual act of a female partner hanging from the male by wrapping her arms around his neck and her legs around his waist, simialr to the position of a sloth hanging from a tree branch. The motion is continued by the male moving his hips in the standard motion for penetration, resulting in 'Slothing'.