1. (n.) An instrument for measuring the velocity, or indicating changes in the velocity, of a moving body or substance.

2. (n.) An instrument for measuring the velocity of running water in a river or canal, consisting of a wheel with inclined vanes, which is turned by the current. The rotations of the wheel are recorded by clockwork.

3. (n.) An instrument for showing at any moment the speed of a revolving shaft, consisting of a delicate revolving conical pendulum which is driven by the shaft, and the action of which by change of speed moves a pointer which indicates the speed on a graduated dial.

4. (n.) An instrument for measuring the velocity of the blood; a haematachometer.

Mach meter accelerometer anemograph anemometrograph anemoscope cock ground log harpoon log log log line patent log speedometer tachometer taffrail log vane weather vane weathercock wind cone wind gauge wind indicator wind sock wind vane wind-speed indicator