Typically the term for older or grown-up, male fans of the "My little Pony" franchise. But since there is no common and nalog term for female fans of the show, brony can as well be used gender-neutral.
random Fan #1: Well, although i am male and grown-up, i actually like wathing this new "My little Pony" show.
rndom fan #2: Don't worry, it's cool! We also do. Welcome to the herd, brony.