It is when a mail (or femile if they have a strap-on) lays there partner on their belly with their butt exposed and jumps in the air and slams their penis into their partners butt
Dude, my gf wanted to do something crazy last night, so I buttnuked her, it was awesome but painful
When one hotdog will not succeed in pleasing one's ass one can proceed by rubberbanding all of the hotdogs in the packagetogether and sitting on them to gain anal stimulation.
Sarah became unsatisfied with one hotdog in her anus so she proceeded to invent the polish buttnuke and use it daily.