Someone who goes over the top with their dress or behavior, usually in a trashy manor, generally related to sexual or drugged out behavior. Drag queens, old hookers, drug addicts, obviously horny people in general, are all pretty much skantless by default
A skantless girl at a bar with her tits hanging out, drunk and obviously looking to get laid.
That same girl with puke on her dress going home with some random guy. Morbidly obese hookers in spandex.
Scandalous behavior makes you skantless.