Quick answer: “Smell a rat” means to suspect something is wrong or dishonest.
Smell a rat means to suspect that something is wrong, dishonest, or not as it appears, often before there is clear proof.
Origin & History
The phrase likely draws on the way cats and dogs can sense a hidden rat before it is seen — sensing trouble before there is clear evidence of it.
The idiom has been used in English for centuries to describe a gut feeling that something isn't right.
Idioms like this are the kind of expression documented in general reference works such as the Cambridge Dictionary, which record how figurative meanings develop in everyday English.
Example Sentences
| Sentence | Context |
|---|---|
| When the numbers didn't add up, the accountant smelled a rat. | Finance, work |
| I smelled a rat as soon as he avoided my question. | Suspicion, conversation |
| Investors smelled a rat and pulled their money out early. | Business, finance |
| She smelled a rat when the deal seemed too good to be true. | Deals, caution |
| The teacher smelled a rat when both essays were identical. | Education |
How to Use It
The idiom is used with ‘smell’ conjugated for tense, and always keeps the fixed singular ‘a rat’, regardless of how many suspicious things are involved.
Common Mistakes
Mistakes to Avoid
smell rats.
smell a rat. — The fixed idiom uses singular ‘a rat’.
smelling the rat.
smell a rat. — Use the article ‘a’, not ‘the’.
smell like a rat.
smell a rat. — The idiom has no ‘like’; ‘smells like a rat’ would be a literal comparison.
Similar Idioms
Practise This Idiom
Practice English Idioms
Use these exercises to master idioms in context:
Want to understand the grammar behind this? Explore our Grammar guides.
Quick Check: Smell a rat
2 questions — test what you just learned.
1. What does “Smell a rat” mean?
2. Complete the sentence: “When the numbers didn't add up, the accountant _____.”
Frequently Asked Questions
What does "smell a rat" mean?
To suspect that something is wrong, dishonest, or not as it appears, often before there is clear proof.
Where does "smell a rat" come from?
The phrase likely draws on the way cats and dogs can sense a hidden rat before it is seen — sensing trouble before there is clear evidence of it.
Can you give an example of "smell a rat" in a sentence?
"When the numbers didn't add up, the accountant smelled a rat." Another: "I smelled a rat as soon as he avoided my question."
Is "smell a rat" formal or informal?
It is informal to neutral, and common in everyday spoken and written English.
What CEFR level is "smell a rat"?
B2. It suits learners who are comfortable with figurative, idiomatic language at this level.
What are common mistakes with "smell a rat"?
A common mistake is saying “smell rats” instead of “smell a rat”. The fixed idiom uses singular ‘a rat’.
What idioms are similar to "smell a rat"?
Related expressions include A red herring, Pull the wool over your eyes, Cry wolf.
Can "smell a rat" be used in writing?
Yes, it appears in blogs, informal articles, and everyday written messages, though very formal writing may prefer a more direct wording.
How do I practise idioms like "smell a rat"?
Use LexFizz Flash Cards and Flip Tiles, and try using "smell a rat" in a sentence of your own to connect the idiom to a real situation.
Does “smell a rat” mean you have proof of wrongdoing?
No, it describes a strong suspicion or gut feeling, not confirmed proof. The suspicion may or may not turn out to be correct.