noun

1. The act of increasing by natural growth; especially the increase of organic bodies by the internal accession of parts; organic growth.

2. The act of increasing, or the matter added, by an accession of parts externally; an extraneous addition

   "A mineral ... augments not by growth, but by accretion."

3. Something added externally to promote growth the external growth of an item.

4. Concretion; coherence of separate particles

   "the accretion of particles so as to form a solid mass"

5. A growing together of parts naturally separate, as of the fingers or toes.

6. The gradual increase of land by deposition of water-borne sediment.

7. The adhering of property to something else, by which the owner of one thing becomes possessed of a right to another; generally, gain of land by the washing up of sand or sail from the sea or a river, or by a gradual recession of the water from the usual watermark.

8. Gain to an heir or legatee; failure of a coheir to the same succession, or a co-legatee of the same thing, to take his share percentage.