trasforming into a wolf would be shapeshifting (and as iv read on the forums twilight didn't have werewolves, just shapeshifters, but i never watched it)
Actual werewolves are mentioned in Breaking Dawn. They're just not featured.
Spoiler
To be a twilight diviner, and to just throw this out there, Twilight does mention actual lycanthropes, but they are not featured in the books. The "werewolves" are Native American shape-shifting telepathic spirit warriors with a shapeshifting gene that kicks in when vampires are near. The "true" werewolves are the animalistic wolfish-men creatures that change during the full moon. They lose their minds upon transformation, killing whatever they can find for nourishment. I believe the Volturi (Italian Vamp Coven) has "quarantined" them from the Americas, which is why they weren't featured.
The above is the information on the Twilight werewolves. Don't read it if you so choose.