What does "suction" mean?

Suction: The act or process of sucking; the act of drawing, as fluids, by exhausting the air. Suction chamber, the chamber of a pump into which the suction pipe delivers. -- Suction pipe, Suction valve, the induction pipe, and induction valve, of a pump, respectively. -- Suction pump, the common pump, in which the water is raised into the barrel by atmospheric pressure. See Illust. of Pump.