a fiesty, mean fat woman who yells at her kids and her husband/boyfriend and it all around pissed off at everything. Think of a mean pig out at gramps farm.
buddy1 "man, that woman across the street is a bitch"
buddy2 "watch out, she's a fiesty bristleback!"
When somebody takes a snow brush, resembling a thick mustache, and continues by vigorously rubbing the bristles across the face of an unsuspecting bystander, thus burning their face.
Jim grabbed the snow brush from his car, walked into the bar and gave Boyle a mean bristle burn.