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”