Dutch thumb
When one inserts his/her thumb in their own ass and then asks a friend/co-worker/boyfriend/girlfriend etc. to smell the thumb.
I hate it when John puts his Dutch thumb in my face.
dutch thumb
When a guy is getting ready to cum and the girl sticks her thumb up the guys butt.
I've never had a better orgasm than when Becky gave me a dutch thumb while she was going down on me.