hot mic

or hot mike

[hot mahyk]

noun Informal.

a microphone that is actively recording or broadcasting, especially if it captures a comment or conversation that the speaker or speakers believed to be private (often used attributively): The techs should limit the number of hot mics to reduce acoustic feedback. The reporter was suspended after her profanity was caught on a hot mic. Their hot mic scheming confirmed the conspiracy theories.

Origin of hot mic

1930–35; hot (in the sense “actively conducting an electric current”) + mic “microphone”