Noun

(en noun)

An elongated depression between hills or mountains, often with a river flowing through it.

* {{quote-magazine, date=2013-08-16, author= John Vidal

, volume=189, issue=10, page=8, magazine=(The Guardian Weekly) , title= Dams endanger ecology of Himalayas , passage=Most of the Himalayan rivers have been relatively untouched by dams near their sources. Now the two great Asian powers, India and China, are rushing to harness them as they cut through some of the world's deepest valleys .}}

The area which drains into a river.

Any structure resembling one, e.g., the meeting point of two pitched roofs.

The internal angle formed by the intersection of two sloping roof planes.

Noun

(en noun)

The act of cleaving or the state of being cleft.

(mineralogy) The tendency of a crystal to split along specific planes.

(biology) The repeated division of a cell into daughter cells after mitosis.

The hollow or separation between a woman's breasts, especially as revealed by a low neckline.

* 1946 , "Cinema: Cleavage and the Code", Time , 5 Aug 1946:

Low-cut Restoration costumes worn by the Misses Lockwood and Roc (see cut) display too much "cleavage " (Johnston Office trade term for the shadowed depression dividing an actress' bosom into two distinct sections).

(chemistry) The splitting of a large molecule into smaller ones.

(politics) The division of voters into voting blocs.