A *really* ugly girl. Not just regular ugly, but seriously busted out in more than one way. So nasty that she could be a stunt-double for Lassie or one of those other dogs in the movies.
Damn, did you see the nasty-looking chick who walked out of your boy's place this morning? He must have been drunk as hell last night to let her follow him home 'cause she was a straight up stunt dog.