An instrument that measures the speed of the wind or of another flowing fluid. The most basic type of anemometer consists of a series of cups mounted at the end of arms that rotate in the wind. The speed with which the cups rotate indicates the wind speed. In this form, the anemometer also indicates the direction of the wind. ◇ Other anemometers include the pressure-tube anemometer, which uses the pressure generated by the wind to measure its speed, and the hot-wire anemometer, which uses the rate at which heat from a hot wire is transferred to the surrounding air to measure wind speed.