When a woman straddles another person or an object and slides down with their vaginas, leaving a mucousy trail, like a slug. Preferably when the woman is lubricated and shaven.
"She was so kinky she asked me if I was down to be slugged by her. I totally was."
"She was slugging his arm when I walked in..I have never seen anything so disgusting."
"Michael wanted to be slugged in the face by the hooker, unfortunately though, she was a He."