ˈklēvij, -ēj noun
( -s )
Usage: often attributive
Etymology: cleave (II) + -age
1.
a. : the quality possessed by many crystallized substances of splitting readily in one or more definite directions and yielding surfaces always parallel to actual or possible crystal faces
cleavage planes
also : the direction of the dividing plane — compare parting
b. : the structure possessed by some rocks by virtue of which they break more readily and more persistently in one direction or in certain directions than in others — compare schist , slate
2. : the action of cleaving or splitting : the state of being cleft : division ; specifically : a division into distinct and often opposed or hostile groups
a sharp cleavage of fundamental interests that kept farmers and wage earners separate — F.L.Paxson
3. : a fragment (as of a diamond) obtained by splitting
4. : cell division:
a. : the series of mitotic divisions of the egg that results in the formation of the blastomeres and changes the single-celled zygote into a multicellular embryo : segmentation — see determinate cleavage , indeterminate cleavage ; discoidal cleavage , superficial cleavage ; holoblastic , meroblastic
b. : any division belonging to this series
c. : a process of cell formation in which the whole mass of cytoplasm is segmented progressively into small usually uninucleate portions leaving no epiplasm (as in spore formation in certain fungi, especially Phycomycetes) — compare free cell formation
5. : the splitting of a molecule into simpler molecules
hydrolytic cleavage
6. : the depression between a woman's breasts especially when made visible by the wearing of low-cut dresses