A common beach hooker that hangs out at the waterfront all day hoping to snag a man with her 50ft man-pole. Most likely never fully washes all the sand out of her vagina/mangina or bathes otherwise than in the sea water, therefore rendering her skanky and useless to mankind.
2) Also applies to girls who look a bit dirty in all interpretations of the word.
1) Friend - "Hey, there's a sofa in that skip and it doesn't look too bad, shall we grab it?"
Me - "Ewww, what are you on about! It's got stains on it, that is SO skanky!"
2) "Dude, that bird looks WELL skanky, I bet she's been around!"