n., adj. In the broadest definition, someone who finds the idea of anthropomorphic (humanlike) animals, in art, fiction, cartoons, costume, or other media, to be an appealing one. Furries are an extremely diverse group and no one furry may possess all, or any, of the traits typically associated with the group; furries can range from people who are fans of old Warner Bros. and Disney cartoons; people who enjoy portraying anthropomorphic animals in art; people who enjoy imagining what a future, past or alternative world might be like if humans were replaced with or accompanied by anthropomorphic animals; and people who like wearing costume tails, ears and/or animal mascot costumes, to those who feel spiritual connections to animals or to the animal form; those who admire the beauty, power, speed or grace of of the animal form; those who believe they have empathy with or can communicate with animals, for example people who work with them; people who have a great deal of respect for animal welfare; and people who find the concept of anthropomorphic animals enjoyable in a sexual way. (Amongst many, many other things.)
Those who do enjoy the erotic/adult side of furry are, like those who participate in any other sexual fetish or behaviour, almost always harmless in their indulgence of their fantasies, which usually involves erotic art and roleplay, and may involve consenting activities with fellow adults while in costume. Why people get uptight about what is such a cute, silly and affectionate expression of pleasure between two (or more) consenting adults when there's much worse out there to get worked up about such as child abuse, I'll never understand.
It's about fun, people. Try it sometime.
n. Furries often attend conventions.
adj. Furry art incoroprates many diverse forms of media.