Plain English Meaning

A heading instrument driven by a spinning wheel inside it. The spinning wheel holds steady in space, so the heading reading stays smooth and accurate during turns and bumps, unlike the magnetic compass which jumps around. The pilot resets it against the compass every so often.

Full Definition

A flight instrument that displays aircraft heading using a spinning gyroscope rather than magnetic sensing. Because the gyro's spin axis remains fixed in space, the instrument provides a stable, steady heading reference that is unaffected by the turning, pitching, banking, and acceleration errors that disturb a magnetic compass. It must be periodically aligned with the magnetic compass during straight-and-level, , since it has no inherent sense of north and will slowly time.