オフマイク

noun

off-mic; off microphone

Refers to speaking away from a microphone or when a microphone is turned off; used in broadcasting, recording, and stage contexts.

• その発はつ言げんはオフマイクだったので、放ほう送そうには乗のらなかった。

  That remark was off-mic, so it didn't go out on the air.