Fissure

fish′ūr, n. a narrow opening or chasm: a cleft, slit, or furrow: any groove or sulcus, esp. one of the furrows on the surface of the brain, as the longitudinal fi ure separating the hemispheres.— adj. Fi ′ūred , cleft, divided. [Fr.,—L. fi ūra , from findĕre , fi um , to cleave.]