The act of giving a swift blow to the lower back or abdominal region moments before ejacualation in order for the hole being penetrated to tighten for a more desireable climax.
Whlie Johnny was having intercourse with big Janet, he gave her a ferocious punch nut moments before her submerged her in his baby batter.
"Let me give you the run down on Finna Nut. You wanna know what it means bro? You want to know what it MEANS? It means ya *bust'n*, it means YA BUST'N. A FAT ONE. ok now who wants to play some Roblox rap battles with ya boi?"
-Kanye