Ass Sniff
When someone sniffs their ass by using their finger.
"Dude, what the fuck did you just Ass sniffed?"
"N-no.."
"N-no.."
Ass sniff-itis
The smell of ass even when not presently sniffing one; The lingering effects from placing your nostril on someone's sweaty ass hole and deeply inhaling.
Michael was diagnosed with ass sniff-itis after spending the day with his boyfriend.
Sniff ass
Someone who farts under the covers, and they stick their head under to smell their own ass.
You must be really cold. Either that or you farted, you sniff ass!