to draw air audibly up the nose, esp for smelling or for clearing the nasal passages
to smell or inhale (something) through the nose
(+ out) to detect or become aware of (something) by or as if by smelling
sniff at
to regard or treat (something) with contempt or disdain
The offer is not to be sniffed at
sniffer noun
[Middle English sniffen, of imitative origin]