Definitions for "Logic Probe"
a device which is used when testing digital circuits, and it shows the logic state at the selected test point
a device which lets you see if a given contact (tracing, pin on a chip, etc) is high or low (a digital one or zero) or alternating (between one and zero) -- a very handy tool for determining if some component is alive or dead
an electronic device that lights up a red (usually) LED if the probe is touched to battery voltage