english
1
general::
Phrase(s): the smoking gun Fig. the indisputable sign of guilt. (Fig. on a murderer being caught just after shooting the victim.) • Mr. South was left holding the smoking gun. • The chief of staff decided that the the aide should be found with the smoking gun.
McGrawhill's American Idioms And Phrasal Verbs
2
general::
Something that serves as indisputable evidence or proof, especially of a crime. For example, There is no smoking gun in the Oval Office; the President had no role in tampering with the evidence. This expression alludes to the smoke coming from a recently discharged firearm, a normal occurrence until the invention of smokeless powder. [Mid-1900s]
American Heritage Idioms