The Collaborative International Dictionary of English v.0.48:

Werewolf \Were"wolf`\, n.; pl. Werewolves. [AS. werwulf; wer a
   man + wulf a wolf; cf. G. w[aum]rwolf, w[aum]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.
   [1913 Webster]

         The werwolf went about his prey.         --William of
                                                  Palerne.
   [1913 Webster]

         The brutes that wear our form and face,
         The werewolves of the human race.        --Longfellow.
   [1913 Webster] Werk

WordNet (r) 3.0 (2006):

werewolf
    n 1: a monster able to change appearance from human to wolf and
         back again [syn: werewolf, wolfman, lycanthrope,
         loup-garou]

Moby Thesaurus II by Grady Ward, 1.0:

46 Moby Thesaurus words for "werewolf":
   Dracula, Frankenstein, Wolf-man, ape-man, bogey, bogeyman, bugaboo,
   bugbear, demon, devil, devil incarnate, fee-faw-fum, fiend,
   fiend from hell, frightener, ghost, ghoul, harpy, hellhound,
   hellkite, hobgoblin, holy terror, horror, incubus, jaguar-man,
   lamia, monster, nightmare, ogre, ogress, phantom, revenant,
   scarebabe, scarecrow, scarer, specter, succubus, terror, vampire,
   werecat, werecrocodile, werefox, werehyena, werejaguar, werelion,
   weretiger



The Devil's Dictionary (1881-1906):

WEREWOLF, n.  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 and 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 for 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."