Derived from lexeme 'bit', which comes in a variety of inflections (e.g.
bitch) which are used to indicate something's bad or unwanted, it tends to be used by sluts in bars when referring to their slutty friends when they do slutty things.
Slut #1: Look at Rachael, she's giving that bartender a blow-job behind the bar.
Slut #2: Man, what a bitty.
