Plain English Meaning
Cockpit instruments that show whether the aircraft's nose is pointed up, down, or level, and whether the wings are banked left or right. They use a spinning wheel inside that stays steady, so the instrument can show the aircraft's position even when the pilot can't see outside.
Full Definition
Flight instruments that use a spinning gyroscope to display the aircraft's pitch and bank relative to the horizon. The gyro's rigidity in space provides a stable reference, allowing the instrument to show the aircraft's attitude regardless of acceleration, turning, or outside the cockpit.