From The Collaborative International Dictionary of English v.0.48:
Fissure \Fis"sure\, n. [L. fissura, fr. findere, fissum, to
cleave, split; akin to E. bite: cf. F. fissure.]
A narrow opening, made by the parting of any substance; a
cleft; as, the fissure of a rock.
[1913 Webster]
Cerebral fissures (Anat.), the furrows or clefts by which
the surface of the cerebrum is divided; esp., the furrows
first formed by the infolding of the whole wall of the
cerebrum.
Fissure needle (Surg.), a spiral needle for catching
together the gaping lips of wounds. --Knight.
Fissure of rolando (Anat.), the furrow separating the
frontal from the parietal lobe in the cerebrum.
Fissure of Sylvius (Anat.), a deep cerebral fissure
separating the frontal from the temporal lobe. See Illust.
under Brain.
Fissure vein (Mining), a crack in the earth's surface
filled with mineral matter. --Raymond.
[1913 Webster]
From The Collaborative International Dictionary of English v.0.48:
Fissure \Fis"sure\, v. t.
To cleave; to divide; to crack or fracture.
[1913 Webster]