A term usually used to describe a person who is subservient or cannot think for himself in a relationship. These men usually spend their time doing womanly chores and are occassionally allowed to play cricket by their wives in order to rediscover some sort of testosterone.
Wilbur and Cameron can play cricket, but this means they are under the thumb of the MRS at all other times.
When a girl is riding you cowgirl and you put your hands behind your back as if tied up, whilst both of your thumbs are up your own ass as she is riding... grinding your thumbs into your G-Spot.
John: Shirley had me under the thumbs last night Mike: Nice! How awesome is it when they come once and think they’re in control... meanwhile you’ve milked your prostate seven times.
John: Two thumbs up ey!?