Funk & Wagnalls:
Werewolf: (wir-woolf) In European Folklore , a human being transformed into a wolf, or having the power to asume the form of a wolf at will.

A Werewolf is someone who can turn into a wolf, supposedly by a full moon or by will. But not all "Werebeasts" are wolfs. There are some who claim to be othe creatures be it a bear, or fox. Werewolves have also beeen a source of inspiration for Hollywood Movies and Books.

See Also My Lycanthropy Section for more Info