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

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.

Biology��

1. 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.

2. Any of the single cell divisions in such a series.