Cleft/kleft/ Definition 1 of 3Pro Tip 1/3Physical Landforms Use 'cleft' to describe natural openings in geographical features. The mountain's cleft was home to numerous birds. Pro Tip 2/3Narrow Opening 'Cleft' usually suggests a narrow, sometimes deep split. A cleft between the boulders provided a path forward. Pro Tip 3/3Not Man-Made 'Cleft' often implies a natural formation, not something made by humans. The roots of the tree formed a cleft in the earth.