the electrode by which electrons leave an external circuit and enter a device, e.g.:
the positive terminal of a battery: compare anode
the negative electrode in an electrolytic cell
the electrode in a thermionic valve or similar electronic device that emits the electrons
cathodal /kəʹthohdl/ adj
cathodic /kəʹthodik/ adj
[Greek kathodos way down, from kata- cata- + hodos way]