fissure
noun [ C ] uk/ˈfɪʃ.ər/ us/ˈfɪʃ.ɚ/
（岩石或土地的）裂缝，裂隙
a deep, narrow crack in rock or the earth
medical specialized（大脑皮层等的）裂纹，沟
a long, deep, narrow hollow area in a surface in the body, especially in the cerebral cortex (= the surface of the brain)
medical specialized（牙齿表面的）裂;疵点
a fault on the surface of a tooth