Pronunciation: (kō"ärk-tā'shun),[key] —n. 1. Pathol. a. a narrowing of the lumen of a blood vessel.
b. a congenital anomaly of the heart in which there is a narrowing of the aorta, resulting in abnormal blood flow.
2. Entomol.the condition of having the body enclosed in a hardened shell or puparium.