2. n. 
A device for measuring in-situ the velocity of fluid flow in a well, usually one completed for production or injection. The most common device is the spinner flowmeter, but torque flowmeters and crosscorrelation flowmeters also are used. In the 1940s and 1950s, various other surface-metering techniques were tried, but spinner flowmeters emerged as the most suitable for measuring downhole velocities. Spinner and torque flowmeters measure the average velocity of the fluids crossing the device, while crosscorrelation flowmeters measure the velocity of a particular phase. Although not normally called flowmeters, various other techniques measure flow velocity, for example water-flow logs, phase-velocity logs, distributed-temperature logs and even audio measurements.