Pitot tube:
"It's a slender tube that has two holes on it. The front hole is placed in the airstream to measure what's called the stagnation pressure. The side hole measures the static pressure. By measuring the difference between these pressures, you get the dynamic pressure, which can be used to calculate airspeed".
To pick a nit: The above would be a pitot/static tube, mostly used on small aircraft. In larger aircraft the little hole in the side is a drain, the pressure loss from that is allowed for. The static measurement hole is in a flat plate, a large and very well engineered sensor.