Definition of: accretion

(ə·krẽ′shən) noun
1. Growth or formation by external additions; increase by adhesion or inclusion; an accumulation or external addition; matter added.
2. Pathol. Abnormal adhesion or growing together.
3. Law Increase, as of land along the seashore or a river, by deposit of alluvium.
4. Increase by natural growth.
5. Geol. The enlargement of rock masses and inorganic bodies by the addition of new material.
—ac·cre′tive adjective