means In folklore, a person who transforms—usually under a full moon—into a wolf or a monstrous wolf-human hybrid, often against their will.

from From Old English 'werewulf,' a marriage of 'wer' meaning 'man' (the same ancient root that gives Latin 'vir,' as in 'virile') and 'wulf,' simply 'wolf.' So the word is bluntly literal: man-wolf. That 'wer-' for 'man' survives almost nowhere else in modern English—it slunk off into the night like the creature it names, leaving 'werewolf' as its last famous hiding place. The Greek-flavored term 'lycanthrope' (from 'lykos,' wolf, plus 'anthropos,' human) is a later, fancier cousin meaning the same thing.