When you stick the head of your penis in a persons rectum while the person needs to defecate and then pull out, offering them the choc-top for $1 at the drive thru.
it is when you have anal sex with someone, then pulling out your penis which is covered in their shit and then getting your shit covered penis sucked, blowjob.
After having anal sex
Matilda: wow that was great
Nathaneal: ready for desert?
Matilda: mmm... is it your choc top?