(1) A switch that is opened or closed. See
switch.
(2) A group of transistors that makes up an AND, OR or NOT Boolean logic gate. See
Boolean gates,
logic gate and
gate array.
(3) In a field-effect transistor (FET), the gate is the element that acts as a trigger to cause the transistor to switch. In a bipolar transistor, the gate is called the "base." See
transistor,
FET and
MOSFET.
The Gate in an NMOS Transistor
The gate is the trigger line. When pulsed, an electromagnetic field causes the switch to close.