A long and calculated sniff, usually of young girls. It's named after Joe Biden who's documented to have sniffed several young girls and women while in the presence of cameras.
Man, I didn't like how Dan took a few Biden sniffsoff that girl. It was gross.
The complex series of highly coordinated movements Joe Biden skillfully executes in order to sniff the hair of an unwitting teenage female. The careful dance involves first the scooping of his face towards the female's hair, then the titular sniffing action that allows him to inhale her fragrance.