Butt thumbing is much likebutt fingering, except that the thumb is used. It tends to be more intense because of the dexteral advantage of the thumb over fingers for two main reasons:
1. The thumb does not have other fingers getting in its way
2. It is much sassier
starting now, every chick i bone is gonna experience the buttthumb too
When you're fucking a chick minding your own business and a bitch sticks her thumb up your ass, so you slap the shit out of her and throw her nasty ass to the curb.
"That girl's hot but she tried to give me buttthumb,and now I might be gay"