Definition of "backplate"

A plate protecting a fighting person's back.  quotations  examples

(underwater diving) A plate harnessed to a diver's back, to which the gas cylinders are attached.  examples

A metal plate on the rear of a computer's casing, used to cover a port or slot.  examples

A wood or metal (or glass, etc) plate that serves as a backing for an object.  examples

(UK, automotive) A rigid metal plate inside the brake drum, which supports the wheel cylinder, brake shoes, and other parts of a drum brake.  examples

Part of a condenser microphone that sits behind the diaphragm and which acts, in conjunction with the diaphragm, as a sort of variable capacitor.  examples