A furry is a fan of cartoon animals, especially one who draws and enjoys pics of animals behaving like people, or who wears animal costumes.
Some furries see this - hiding in a costume which is shaped by their own identity - as a form of rebellion against social norms that would had destroyed their own precious identity. Some go as far as do acts like these for their own amusement or self-pleasure, ignoring others’ rightly-disgusted reactions just to defy society and have a good laugh.
Although I kinda like the animal costumes, the furry fandom can be arrogant pricks.
