A derogatory term that befits individuals who find pictures of anthropomorhpic creatures erotic and / or awe-inspiring.
Unfortunately there is no one definition for a furry, so this will break down the stages that a human goes through to become a furry:
1. An individual finds a species of animal particularly interesting or beautiful, and begins to seek works that include this animal. This may range from artwork, books, or fiction from various authors. No quirks have been noted at this stage, but the individuals affection with the creature begins to grow beyond the bounds of admiration and into something far, far more sinister.
2. The individual meets other individuals who share a common ground with the animal in question. They begin to discuss in great detail about the animal and aspects of the animal they find fascinating. They may go so far to say that they would like those aspects as a part of themselves. They begin to find or make works of their own about the creature, becoming more and more detailed with each project. Admiration slips into affection, and from affection to pure, raw, lust.
(Note that at this stage the furry is still of a human mind, though slightly bewildered. Most furries are at this stage.)
3. The individuals expresses a unnatural desire for the animal in question. To appease their increasing need for self-satisfaction, the individuals find or make works of the animal in a human-esque form, usually in poses that most rational people would find questionable. The individuals go so far to say that they require sexual release from these creatures, and speak of their animal on a daily if not hourly basis. Their mind derails all forms of rational thought and replaces it with the animal. They shelter themselves from the outside world and delve deeper into their circle of e-friends. Most furries at this stage appear human from a distance, and mayhaps even up close, but conversations with them tend to rival the witty banterings of the insane, ranging from random outbursts about their love of the animal to their need to find more people who wish to talk about how they love their animal. Most conversations may or may not include the words 'yiff', 'vore', or 'Yahoo Groups'.
4. Any aspects that made up the furrys former sanity crumble as they are now completely detached from the sentient world. They ARE the animal in all respects. They find solace in extremely erotic pictures of the animal with other animals, doing things both consensual, non-consensual, and most of the times outright acts of unbelieveable terror that rational humans would find horrifying and grounds of lunacy. They also may wear full-body makeup or a costume or the animal in question, and engage in physical acts within their circle of friends. Not all furries, however, are that extreme at the practice. Eventually they consider themselves members of some sound religion that is under fire of prejudice, and they lash out at any and all anti-furry activists (humans) as it threatens their sheltered lifestyle and could possibly shatter their imaginary world. They begin to think of themselves as the only sentient beings, when in actuality the clowns are running the circus in their fantasy world of shitting dicknipples and transvestite dogs. Any and all form of human interaction with a furry at this stage is impossible or considered an act of anti-furry terrorism that is met with an explosion of outrage and extreme argumentation, usually over the internet. Some are so serious in their practice that they undergo incredible surgeries to graft a part of their animal (ears, tail, whiskers, shitting dicknipples) onto themselves.
(Note that this stage is the most dangerous and should be recommended for immediate execution, sterilization, or possible exhibit at the local zoo.)
The Wrong Example: "That man owns a copy of The Lion King, and is therefore a furry."
The Right Example: "That man owns a centerfold of simba / mufasa incest, and is therefore a furry."