<p><strong>Noun</strong></p><ul><li>a narrow opening produced by cleavage or separation of parts.</li><li>cleavage (def 1).</li><li>Anatomy: a natural division or groove in an organ, as in the brain.</li></ul><p><strong>Verb</strong> (used with object)</p><ul><li>fis·sured, fis·sur·ing: to make fissures in; cleave; split.</li></ul><p><strong>Verb</strong> (used without object)</p><ul><li>fis·sured, fis·sur·ing: to open in fissures; become split.</li></ul>