Plain English Meaning
A gauge that shows how hot the gases are between the spinning turbine wheels inside the engine, so the pilot can make sure the engine is not running too hot.
Full Definition
A cockpit instrument that displays the temperature of the gases flowing between the turbine wheels of a turbine engine, measured by thermocouples placed in the gas path between stages of the turbine section. It is used to monitor engine operating temperature against published limits during start, acceleration, and continuous operation.
Context Anchor
Seen on turbine-powered aircraft during engine start, takeoff, climb, and any power change where must be watched.