sniff

• short inhalation through the nose; sound of a sniff; odor, scent
inhale through the nose; smell; express disapproval by making a sniffing sound; take into the the nose by inhaling; perceive, sense
when you sniff, you breathe in air noisily through your nose, for example when you have a cold, or are trying not to cry. verb here but can also be used a count noun. e.g. the classroom rang with coughs, sniffs, and sneezes.
if you sniff something, you smell it by breathing in through your nose. verb here but can also be used a count noun. e.g. he took a cautious sniff.
if someone sniffs a substance such as glue, they deliberately breathe it in order to feel the effects of it.
you can use sniff to indicate that someone is saying something in a superior or contemptuous way.
if you sniff something out, you discover it, often after a search or by guessing where it might be; an informal expression.