Definition
The spinning motion of a gyroscope's rotor about its spin axis, which gives the gyro its rigidity in space and makes it useful as a reference for flight instruments. In a turn coordinator, the rotor's spin axis is canted upward about 30 degrees from the longitudinal axis, so the gyro senses both roll and yaw rates rather than yaw alone.
Plain English
The fast spinning of the small wheel inside a gyro instrument. That spinning is what lets the instrument hold a steady reference and show the pilot what the airplane is doing.
Context Anchor
Seen in discussions of gyroscopic instruments, especially how the turn coordinator works.
Derivation
Gyro comes from the Greek gyros, meaning a ring or circle. Rotation comes from the Latin rotare, to turn. Together the term simply describes a wheel turning in a circle at high speed, which is exactly what a gyro rotor does.
Why Pilots Care
Without sustained gyro rotation the turn coordinator cannot provide reliable rate-of-turn information, affecting instrument interpretation during partial panel flight.
Analogy
A fast-spinning bicycle wheel tends to stay steady and resists being twisted. A gyro uses that same basic idea inside the instrument.
Intuition Check
Do not confuse gyro rotation with takeoff rotation, where the pilot raises the nose for liftoff. Here, rotation means the spinning motion inside the gyroscopic instrument.
Example Sentence 1
After engine start, the pilot waited a few moments for gyro rotation to spin up before trusting the attitude and turn indications.
Example Sentence 2
Loss of electrical power stopped gyro rotation and rendered the turn coordinator unusable.