Distortion that occurs in sound reproduction as a result of undesired speed variations during the recording, duplicating, or reproducing process.

A fast-changing variation in received signal strength, such as may be caused by antenna movements in a high wind or interaction with a signal or another frequency.

The irregular alternating motion of the parts of a relief valve due to the application of pressure where no contact is made between the valve disk and the seat.

aeronautical flutter.

Rapid, regular contraction of the atrial muscle of the heart.