Definitions for dead air
Random House Webster's College Dictionary
the loss or suspension of the video or audio signal during a television or radio transmission.
Category: Radio and Television, Showbiz
Origin of dead air:
an inadvertent interruption in a broadcast during which there is no sound
An unintended interruption in a radio broadcast during which there is no sound; a similar interruption of a television broadcast in which there is neither sound nor a video signal.