noun
Etymology: Latin circus (circle)
1. : involuntary circling in one direction due to injury to the central nervous system, especially to the cerebellum or the semicircular canals — compare nystagmus
2. : movement of a wave of excitation through excitable tissue in such a manner that it makes and repeats more or less indefinitely a complete circuit back to the point of origin, considered to be a possible cause of auricular fibrillation in man