To smell a rat is to sense that something dishonest is going on. Begin to smell a rat, I smell a rat, they smell a rat.
It is suspicion without proof, which is exactly the state the phrase names. The picture is of a dog or a cat catching a scent it cannot see.
1phrasesmell a ratTo sense that something dishonest is going on.
“When the figures came in twice she began to smell a rat.”
smell a rat is a phrase.
Practised in Idioms