[ noun ] a monster able to change appearance from human to wolf and back again <noun.person>
Werewolf \Were"wolf`\, n.; pl. {Werewolves}. [AS. werwulf; wer a man + wulf a wolf; cf. G. w["a]rwolf, w["a]hrwolf, wehrwolf, a werewolf, MHG. werwolf. [root]285. See {Were} a man, and {Wolf}, and cf. {Virile}, {World}.] A person transformed into a wolf in form and appetite, either temporarily or permanently, whether by supernatural influences, by witchcraft, or voluntarily; a lycanthrope. Belief in werewolves, formerly general, is not now extinct.
The werwolf went about his prey. --William of Palerne.
The brutes that wear our form and face, The werewolves of the human race. --Longfellow.