a dumbass bitch, usually 18 or younger. picture it: short shorts, ugg boots, string straight hair and mad eye makeup for a high school frosh. they go out at night looking for the party so they can get shitty on mikes hard, cheap wine, or other people's alcohol. they have a bun on the top of their head as if they rolled out of bed looking like a pre-pubescent prostitute. being a biddy means being dumb is the cool thing to do.
"look at all those god damn biddies. i can see her tities through that sheer ass abercrombie shirt."