Typically refers to 13-30 year old male fans of the 2010 reboot of the show My Little Pony: Friendship is Magic, but may also include females (see fillies).
Brony = Bro + Pony
While generally associated with a negative stereotype by outsiders, due to it's former 80's frilly girly-girl twinkle-toed tea-parties and all-female main casting, bronies are attracted to the new show by it's good animation, acting, writing, and humor.
Having once been on the outside, bronies can love and tolerate others until they themselves become bronies. However, haters gonna hate— most likely due to the fact that they have a masculinity inferiority complex, where they believe that if they watched My Little Pony, others like them will label them as an effeminate freak.
Phase 1) Are you joking? How can adult males watch a show for girls?
Phase 2) Pfft. I'll see what all the fuss is about, maybe make fun of the show.
Phase 3) Meh. It was okay. It wasn't that bad, I'll give it that.
Phase 4) It's actually kind of funny and entertaining.
Phase 5) I take back everything bad I've said! This is AWESOME! ...but I'd be ruined if anyone found out...
Phase 6) Friendship is Magic! Screw it! I'm a brony!
Phase 7) I'm dead serious, you should watch My Little Pony, too.
Hater) You guys are all gay freaks... I'll never watch that. Now if you'll excuse me, I need to jerk off while lifting weights and playing video games all day to pretend to be a man.