fissura fis·su·ra (fĭ-s&oobreve;r'ə, -sh&oobreve;r'ə) n. pl. fis·su·rae (-s&oobreve;r'ē, -sh&oobreve;r'ē)
A deep fissure, cleft, or slit.
A particularly deep sulcus of the surface of the brain or spinal cord.