A member or ex-member of the furry fandom who has been burned in some severe way. Usually this is a result of some event or other portion of the fandom that has offended them enough that they feel their viewpoint of what the fandom should be is correct. They are passionate in their views and usually attempt to speak out strongly against whatever they feel is against their moral statutes. They see the furry fandom has acquired an ugly front and seek to remedy this and make the fandom more "family friendly" by removing all the "bizarre" or possibly illegal portions of the fandom from the public eye, or altogether entirely.
That guy over there is protesting against indecent furry art, but he is dressed like a cat; he must be a burned fur.
A failed attempt to "improve" furry fandom, comprised largely of well-intentioned furries but lacking any real direction. The whole business collapsed when the members turned on eachother and a few went nuts.
See that troll on Portal of Evil? He was a burned fur once, before he went crazy.