1. An electronic switch that is the elementary component of a digital circuit. It produces an electrical output signal that represents a binary 1 or 0 and is related to the states of one or more input signals by an operation of Boolean logic, such as AND, OR, or NOT. Also called: logic gate. See also gate array.
2. The input terminal of a field-effect transistor (FET). Also called: gate electrode. See also drain (definition 1), FET, MOSFET, source (definition 2). 3. A data structure used by 80386 and higher microprocessors to control access to privileged functions, to change data segments, or to switch tasks.