accretion (Noun) — An increase by natural growth or addition.
accretion (Noun) — Something contributing to growth or increase. ex. "he scraped away the accretions of paint" ex. "the central city surrounded by recent accretions"
accretion (Noun) — (astronomy) the formation of a celestial object by the effect of gravity pulling together surrounding objects and gases.
accretion (Noun) — (biology) growth by addition as by the adhesion of parts or particles.
accretion (Noun) — (geology) an increase in land resulting from alluvial deposits or waterborne sediment.
accretion (Noun) — (law) an increase in a beneficiary's share in an estate (as when a co-beneficiary dies or fails to meet some condition or rejects the inheritance).