The idiom "smoking gun" refers to a piece of evidence that proves someone's guilt beyond any doubt. It is often used in legal or political contexts when a piece of evidence is discovered that clearly shows who is responsible for a crime or wrongdoing.
The term "smoking gun" comes from the idea that when a gun is fired, it produces smoke. If someone is caught with a smoking gun, it is clear that they were the one who fired it. Similarly, when a piece of evidence is discovered that is so incriminating that it leaves no doubt about who is responsible, it is referred to as a "smoking gun."
For example, if a politician is accused of taking bribes, a smoking gun might be a recorded conversation in which they are heard accepting money in exchange for political favors. In a court of law, a smoking gun might be a DNA sample that matches the suspect's DNA to the crime scene.
In everyday conversation, the term "smoking gun" can also be used more broadly to refer to any piece of evidence that is particularly convincing or damning.
• The detective found the smoking gun at the scene of the crime.
• The whistleblower's testimony provided the smoking gun that exposed the government's corruption.
• I don't understand what "smoking gun" means.
• The report presented a smoking gun that revealed the CEO's embezzlement of company funds.
• The DNA evidence was the smoking gun that helped convict the suspect.
• The leaked email was the smoking gun that proved the company was involved in illegal activities.