Plain English Meaning
An instrument that shows which direction the aircraft is pointing, using a fast-spinning wheel inside to keep the reading steady while the magnetic compass would be swinging or lagging.
Full Definition
A flight instrument that uses a spinning gyroscope to display the aircraft's heading on a rotating compass card, providing a steady, drift-free reference unaffected by the turning, banking, and acceleration errors that disturb a magnetic compass.
Context Anchor
Seen in instrument flying when maintaining headings, turning to assigned headings, and scanning the flight instruments.