1. An electric lead that connects to a measuring or monitoring circuit, or contains such a circuit at its end or along its length, and that is used for testing purposes. The measuring or monitoring circuit may be formed from either active or passive components.

2. A means of testing integrated circuits or devices while they are still on the complete semiconductor wafer, prior to dicing. The probes provide mechanical and electrical connection to the bond pads that are usually found around the periphery of the IC. The probes can be moved individually to the correct locations on the wafer – these are known as micromanipulator probes – or they can be mounted onto a probe card in a fixed location that reflects the arrangement of the bond pad connections around the particular IC.

3. A resonant conductor that is inserted into a waveguide or cavity resonator in order to inject or extract energy.