1. any gradual increase in size, as through growth or external addition
2. something added, especially extraneously, to cause growth or an increase in size
3. the growing together of normally separate plant or animal parts
4. pathology .
a. abnormal union or growing together of parts; adhesion
b. a mass of foreign matter collected in a cavity
5. law . an increase in the share of a beneficiary in an estate, as when a co-beneficiary fails to take his share
6. astronomy . the process in which matter under the influence of gravity is attracted to and increases the mass of a celestial body.