Definition of Gyrus

Gyrus: A convolution on the surface of a cerebral hemisphere caused by the infolding of the cerebral cortex. The gyri are bounded by crevices in the cortex called sulci. Many gyri are constant enough in their occurrence as anatomic features that they have been given names as, for example, the cingulate gyrus, the dentate gyrus, and so on. From the Greek gyros = a circle.

Source: MedTerms™ Medical Dictionary
http://www.medterms.com/script/main/art.asp?articlekey=32261
Last Editorial Review: 6/14/2012