1. In an electron tube, the valence of the anode current which does not further increase with an increase in anode voltage.

The term anode is a general term for the electrode, terminal, or element through which current enters a conductor; so called from the path the electrical current was thought to take.

2. A situation in which the anode current of an electron tube can not be further increased by increasing the anode voltage.

The electrons are then being drawn to the anode at the same rate as they are emitted from the cathode.