Cutie Mark 

The symbols marking the hindquarters of My Little Pony characters, particularly those of the fourth generation (see My Little Pony: Friendship is Magic). A cutie mark usually gives some indication of a pony's special talent, profession, or personality.

Fluttershy's cutie mark is a trio of butterflies because her special talent relates to animals.

Cutie Mark by chronicLurker February 27, 2012

Cutie Mark 

A Cutie mark is a picture/tattoo on someone's body to state their special talents. It does not always have to be related to Friendship is Magic, but the word got popular from it.

Person 1: If I could have a cutie mark it would show a paintbrush
Person 2: I would have a controller.

Cutie Mark by translant December 25, 2015

Cutie Mark Play 

Cutie Mark Play is a sexual term created by the My Little Pony: Friendship Is Magic fandom, this term originated from the season 5 premier staring Starlight Glimmer involving taking a pony's cutie mark.
It's while in sexual intercourse, you take the pony's cutie mark while you plow them, stripping them of anything special about them making them useless and powerless, its a form of domination and degradation, where they are useless and put under your control during sexual intercourse.

This kink already has a small group of supporters, usually those who are also into extreme BDSM, degradation, humiliation, and dominance.

My wife is a kinky fuck, she's in to this thing called "cutie mark play" it's some kind of weird dominance thing.

Cutie Mark Play by proud_BG_brony October 27, 2015