look up any word, like timebomb:
 
1.
A bad-ass fucking pony from My Little Pony: Friendship is Magic. She'll make a dress faster than you, and whine about how you take long to do it. And laugh in your face like this. "BwaHA-HA!"
Guy 1: "Dude, Rarity was awesome in that last episode!"
Guy 2: "I thought Fluttershy was pretty cool in it too."
Guy 1: "LOL"
by BRONYBRONY August 30, 2011
 
2.
A girl that is both smart and hot. It is rare to find a girl like this so thus, rarity.
Kara, Jason's date to HC is a rarity.
by jewboy95120! September 25, 2009
 
3.
A fucking pony goddess. Rarity is the fashionista of the show 'My Little Pony: Friendship is Magic'. Rarity's element may be generosity, but that is only a short word in a long list of many. She is kind, generous, fashionable, loving, loyal, and a great singer. She lives for her friends and her fashion. In short, if you ever meet a Rarity, consider yourself lucky.
Pinkie Pie: Oh my Celestia, Rarity is so cool, and sooo nice.
Spike: I know. 😍
by Rarity_11 July 12, 2014
 
4.
This relates to the Pony "Rarity" from the series "My Little Pony: Friendship is Magic". It is a term given to a girlfriend or ex-girlfriend when she becomes super bitchy and complains a lot.
"Man, your girlfriend has been a real Rarity lately."

"Dude, I am so glad you dumped her! She was such a Rarity!"
by Uncle Nerdicus September 21, 2013