scissure
/ˈsɪʃə/ /ˈsɪʃʊə/noun
1 Generally. A cleft or opening made by cutting or separation of parts; a rent, a fissure.
2Chiefly Anatomy and Zoology. A natural cleft, groove, or narrow opening in the surface of the body, an organ, etc.; = fissure. Now rare.
3Division into two parts; cleavage.
Origin
Late Middle English (in an earlier sense). From Middle French scissure, sisure, cissure (French scissure) crack, split, crack or split in the skin, political split or schism, fissure in a bone or bodily organ.