What is "contractile vacuole"

Contractile \Con*tract"ile\, a. [Cf. F. contractile.] tending to contract; having the power or property of contracting, or of shrinking into shorter or smaller dimensions; as, the contractile tissues.

The heart's contractile force.
--H. Brooke.

Each cilium seems to be composed of contractile substance.
--Hixley.

Contractile vacuole (Zo["o]l.), a pulsating cavity in the interior of a protozoan, supposed to be excretory in function. There may be one, two, or more.

Vacuole \Vac"u*ole\, n. [L. vacuus empty: cf. F. vacuole.] (Biol.) A small air cell, or globular space, in the interior of organic cells, either containing air, or a pellucid watery liquid, or some special chemical secretions of the cell protoplasm.

Contractile vacuole. (Zo["o]l.) See under Contractile, and see Illusts. of Infusoria, and Lobosa.

Food vacuole. (Zo["o]l.) See under Food, and see Illust. of Infusoria.

n. (context cell biology English) A vacuole that removes waste or excess water.

A contractile vacuole (CV) is a sub-cellular structure ( organelle) involved in osmoregulation. It is found predominantly in protists and in unicellular algae. It was previously known as pulsatile or pulsating vacuole.