That's "were" as in past tense of "are". As in: "they were wolves, at some point".
The Were-Wolves were wolves before. When a wolf comes to know the desperate depths of starvation, when climate change and desertification have taken all hope of survival away, it might come to be a Were-Wolf.
In places and times when the Sun doesn't rise, the manged, starved thing out of purest desperation will begin to self-cannibalize. It eats itself into an ouroboros, its all-consuming hunger becoming all it is. First it eats its own paws, then its mangy tail, then its hind quarters. And then it's gone. It has become a Were-Wolf then.
Were-Wolves don't exist most of the time. They've starved and degraded past nothing.
They exist now only in the minds of others, as the experiences of wolves, rather than wolves' realities.
Howls in the night. Hungry yellow eyes in the darkness. The patter of paw behind you. Teeth rent through flesh. The Were-Wolf exists only in these states, with no intermediaries and no extremities. There is no wolf, only the eyes and the teeth and that which is conjured first in the mind, not the connecting flesh or the subtleties of anatomy.
Fighting them is difficult as they don't exist in tangible ways. Perhaps one can strike them when they've already bitten through to the bone or into the jugular, as they exist in that definitive state of victory. This countermeasure is undesirable for obvious reasons.
They are afraid of fire, and will not attack those who hold it.
AC: As Leather
Speed: As Wolf
Partially Existent: The Were-Wolf cannot be attacked unless it has recently succeeded on an attack or the wolf has been suspended by some magical paralysis.