A villain or other threat. The allusion is to the traditional story of The Three Little
Pigs, who are menaced one after another in their
respective homes of straw, twigs, and bricks by the
Big Bad Wolf, who seeks to blow the houses down and eat their owners. The tag is often applied to men who have the reputation of being sexual predators.
“I do get a bit tired of being the permanent Big
Bad Wolf ” (Diane Pearson, Voices of Summer, 1993).