An Etymological Dictionary of Astronomy and Astrophysics

A ∩-shaped tube with unequal arms that is used to move a liquid from one level to a lower level via a third level higher than either. Once the short arm is filled, for example, by suction, the liquid flows down in the long arm under the action of gravity due to mass excess in it.

See also: From Fr. siphon, from L. sipho (genitive siphonis), from Gk. siphon “pipe, tube,” of unknown origin.