The term used to describe the fan community(usually of the older group, males and females) of the show My Little Pony: Friendship is Magic.
The term was coined on 4chan's /co/ board.
It is the plural form of 'Brony'
Brony A: "Dude, just finished watching the first season from MLP:FiM!"
Brony B: "Cool! So who do you think is the best pony?"
Brony A mentions the pony they think is best.
Brony B Agrees and exclaims: "Brohoof!"
The bronies brohoof, similar to a high five.