The sexual act of putting your penis into the ass of your partner and making their asshole gape. Then proceeding to put your testicles in their gaping ass and shake them around, like a basketball bouncing around the rim. They do it in Boston all the time.
The religious belief which worships Wombats, stating that they are the masters of everything and the universe, creating the world as we know it, and everything around us. They are the secret masters of knowledge and strength. Only a select few are chosen as the disciples of these mysterious and awesome creatures, everyone else is a follower, united love, and brought together by the belief and spiritual powers of Wombats.
I am convincing a girl in school that i worship wombats, hence the name Wombatism, and this definition.