Pronunciation: (klē'vij),[key] —n. 1. the act of cleaving or splitting.
2. the state of being cleft.
3. the area between a woman's breasts, esp. when revealed by a low-cut neckline.
4. a critical division in opinion, beliefs, interests, etc., as leading to opposition between two groups: a growing cleavage between the Conservative and Liberal wings of the party. 5. the tendency of crystals, certain minerals, rocks, etc., to break in preferred directions so as to yield more or less smooth surfaces (cleav'age planes"). 6. Embryol.the total or partial division of the egg into smaller cells or blastomeres.
7. Also called scission.Chem.the breaking down of a molecule or compound into simpler structures.