1.
If you sniff out something, you discover it after some searching. ( INFORMAL )
...journalists who are trained to sniff out sensation or scandal.
PHRASAL VERB : V P n (not pron)
2.
When a dog used by a group such as the police sniffs out hidden explosives or drugs, it finds them using its sense of smell.
A police dog, trained to sniff out explosives, found evidence of a bomb in the apartment.
PHRASAL VERB : V P n (not pron) , also V n P