An emitter overload was a malfunction in a starship's deflector shield system. If one of the emitters in the shield grid suffered such an overload, the deflectors would fail to function, leaving the ship vulnerable to attack and unable to prevent transporter beaming in or out.

In 2384, an Orion spy utilizing the identity Een Norgadd aboard the USS Newton claimed to have implanted a system interrupt that would trigger a an emitter overload if the shields were raised. (TNG eBook: The Stuff of Dreams)