Women who you've seen more of their cooch than your own.
Usually girls who pose in a squat or let photographers take such revealing angles like that. You would think they may be advertising said cooch.
a) Could be literally talking about a model
b) Or just an extreme alternative to "hussy"
Completely unrelated to porn.
Sometimes suicide girls, gravure models, tumblr camwhores, etc.
Also, joking around with friends: "Girl, your skirt is too short, don't be a cooch model!"