The Collaborative International Dictionary of English v.0.48:

Gyri \Gy"ri\ (j[imac]"r[imac]), n. pl.
   See Gyrus.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Gyrus \Gy"rus\ (j[imac]"r[u^]s), n.; pl. Gyri
   (j[imac]"r[imac]). [L. See Gyre, n.]
   A convoluted ridge between grooves; a convolution; as, the
   gyri of the brain; the gyri of brain coral. See Brain.
   [1913 Webster]