The book series "The Wheel of Time" frequently talks about characters "sniffing" at someone.
Here are a few examples:
“ ‘Poke the meekest dog too often,’ “ Elayne quoted, “ ‘and he will bite.’ Not that Lan is very meek.” She got a sharp look and a sniff from Nynaeve.
Or this one:
Her smile became a grin that made Elayne sniff disapprovingly
It doesn't seem natural to think of someone inhaling air through their nose in these situations... So what does it really mean?