A machine where a static pressure rise is obtained by allowing successive volumes of gas to aspired into and exhausted out of a closed space by means of the displacement of a moving chamber.
In a positive displacement compressor, operating on the principle of a piston (shaped rotor or rotor with blades) moving in a closed cylinder (housing), the decreasing volume of air causes an increase of the pressure in the cylinder.
(See also, ‘Air compressors types (based on compression method) in industry’)