look up any word, like sex:
 
1.
A tantric sexual position in which the man sits cross-legged and the woman sits in his lap, facing him, with her legs wrapped around his hips.

It has absolutely nothing to do with Jenna Jameson.
In the novel The Dharma Bums, zen lunatic Japhy Ryder engages in long sessions of yabyum with various girls.
by littleksun September 26, 2007
 
2.
1. to engage in extreme sexual indulgence, most often incorporating a religious element; 2. such indulgence
Jenna Jamison often engages in yabyum, with one man entering her from behind, while she sucks off another
by DJ Gargamel July 28, 2006