The act of sexual forplay after ejaculation. But in this case it's a post-forplay after a round of seamen release. One must continue the act of sexual inter course or oral sex.
"Oh, baby I just cummed". Go ahead and get nasty with it to get me going again.
Big'n'Nasy describes the act of cumming into a womans, or mans mouth then proceeding to shit in their mouth also. After this, you make-out with the person with the cum/shit mixture and swap back and forth swallowing a little of the matter each time until it's entirely gone. Similar to snowballing
Guy1: Dude...I did a Big'n'Nasty with Victoria last night.
Guy2: Yea, I can tell...I can smell the shit on your breath.