What is the meaning of cleavage?

noun

• The state of being split or cleft.
  • usage: "there was a cleavage between the liberal and conservative members"
• The breaking of a chemical bond in a molecule resulting in smaller molecules.
• Embryology) the repeated division of a fertilised ovum.
  • synonyms: segmentation
• The line formed by a groove between two parts (especially the separation between a woman's breasts. )
• The act of cleaving or splitting. .