Fissure

(fish'ŭr), n. [Lat. fissura, Fr. fissure, It. fissura, fessura, Sp. fissura. See FISSILE.] A cleft; a narrow chasm made by the parting of any substance; a longitudinal opening; as, the fissure of a rock.

Fissure of Sylvius (Anat.), a deep depression or fold inward from the surface on each side of the brain, dividing the anterior and middle lobes of the cerebrum.—Great fissure of Bichat, a depression connecting these two fissures across the brain in a curve backward.