noun

1. a cleaving, splitting, or dividing
2. the manner in which a thing splits
3. a cleft; fissure; division
4. the hollow between a woman's breasts, as made visible by a low-cut neckline
5. Biol.
   1. cell division, esp. the series of mitotic cell divisions that transform the fertilized ovum into the earliest embryonic stage
   2. any single division in this series
6. Mineralogy the tendency of some minerals to break in definite planes, producing smooth surfaces