The Devil's Dictionary: Werewolf
A wolf that was once, or is sometimes, a man. All werewolves are of evil disposition, having assumed a bestial form to gratify a beastial appetite, but some, transformed by sorcery, are as humane as is consistent with an acquired taste for human flesh.
Some Bavarian peasants having caught a wolf one evening, tied it to a post by the tail and went to bed. The next morning nothing was there! Greatly perplexed, they consulted the local priest, who told them that their captive was undoubtedly a werewolf and had resumed its human form during the night. "The next time that you take a wolf," the good man said, "see that you chain it by the leg, and in the morning you will find a Lutheran."