A pitot tube is used by aircraft to measure their approximate velocity. Pitots can be heated to set the incoming air to a referenced temperature. The pressure is routed to a sensor, and the velocity is calculated. This information can be used as an input to the flight computer or as a standby in case the more accurate doppler system goes down in military aircraft. Modern pitots closely resemble machine gun barrels in appearance.

I think this definition was a little after Webster 1913's time.