Definition
Flight instruments that use a spinning rotor (gyroscope) to sense and display the airplane's attitude, heading, or rate of turn. The three traditional gyro instruments are the attitude indicator, the heading indicator, and the turn coordinator (or turn-and-slip indicator). They are powered either by engine-driven vacuum or by electricity.
Plain English
Cockpit instruments that work using a fast-spinning wheel inside them. That spinning wheel keeps a steady reference, which lets the instrument show how the airplane is banked, pitched, turning, or heading.
Context Anchor
Seen during the cockpit portion of preflight, after engine start, during taxi checks, and anytime the pilot is checking the airplane’s flight instruments.
Derivation
From the Greek gyros, meaning 'circle' or 'turn.' A gyroscope is literally a 'turning thing.' The name fits because these instruments rely on a wheel spinning in a circle to do their job.
Why Pilots Care
They supply reliable attitude and heading data when visual references are unavailable, allowing continued safe flight in clouds or at night.
Analogy
A spinning toy top tends to stay pointed in the same direction while it spins. A gyro instrument uses that same basic idea to give the pilot a steady reference inside a moving airplane.
Intuition Check
Gyro instruments are not simply any round cockpit instruments. The term means instruments that use a gyroscope, or a modern electronic equivalent, to sense and display aircraft movement or position.
Example Sentence 1
During the preflight assessment, the pilot checked that the gyro instruments were uncaged and showing reasonable indications before taxi.
Example Sentence 2
Once in the clouds the pilot cross-checked the gyro instruments to keep the wings level and maintain heading.