An American holiday that occurs on or around Halloween during which women get tarted up and dress as slutty nurses, slutty cops, slutty superheroes, slutty schoolgirls, slutty cats, slutty cowgirls, slutty cheerleaders, etc.
For National Dress Like a Slut Day, my girl wore a pointy hat and a black bikini with her tits and ass hanging out and said it was a witch costume.