What does "contractile" mean?

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 (Zoöl.), a pulsating cavity in the interior of a protozoan, supposed to be excretory in function. There may be one, two, or more.