- the act of cleaving or splitting.
- the state of being cleft.
- the area between a woman's breasts, especially when revealed by a low-cut neckline.
- 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.
- the tendency of crystals, certain minerals, rocks, etc., to break in preferred directions so as to yield more or less smooth surfaces (cleavage planes).
- Embryology. the total or partial division of the egg into smaller cells or blastomeres.
- Also called scission. Chemistry. the breaking down of a molecule or compound into simpler structures.
Origin of cleavage
- informal the separation between a woman's breasts, esp as revealed by a low-cut dress
- a division or split
- (of crystals) the act of splitting or the tendency to split along definite planes so as to yield smooth surfaces
- Also called: segmentation embryol (in animals) the repeated division of a fertilized ovum into a solid ball of cells (a morula), which later becomes hollow (a blastula)
- the breaking of a chemical bond in a molecule to give smaller molecules or radicals
- geology the natural splitting of certain rocks, or minerals such as slates, or micas along the planes of weakness
The sense of "cleft between a woman's breasts in low-cut clothing" is first recorded 1946, defined in a "Time" magazine article [Aug. 5] as the "Johnston Office trade term for the shadowed depression dividing an actress' bosom into two distinct sections;" traditionally first used in this sense by U.S. publicist Joseph I. Breen (1888-1965), head of the Production Code Administration (replaced 1945 by Eric Johnston), enforcers of Hollywood self-censorship, in reference to Jane Russell's costumes and poses in "The Outlaw."
- A series of cell divisions in the ovum immediately following fertilization.segmentation
- The splitting of a complex molecule into two or more simpler molecules.scission
- The linear clefts in the skin, indicating the general direction of the fibers in the dermis.
- Geology The breaking of certain minerals along specific planes, making smooth surfaces. These surfaces are parallel to the faces of the molecular crystals that make up the minerals. A mineral that exhibits cleavage breaks into smooth pieces with the same pattern of parallel surfaces regardless of how many times it is broken. Some minerals, like quartz, do not have a cleavage and break into uneven pieces with rough surfaces.
- The series of mitotic cell divisions by which a single fertilized egg cell becomes a many-celled blastula. Each division produces cells half the size of the parent cell.
- Any of the single cell divisions in such a series.