What is the meaning of Accretion?

Increase by natural growth, especially the gradual increase of organic bodies by the internal addition of matter; organic growth; also, the amount of such growth.

(Gradual) increase by an external addition of matter; an instance of this.

The process by which material is added to a geological feature; specifically, to a tectonic plate at a subduction zone.

Followed by of: external addition of matter to a thing which causes it to grow, especially in amount or size.

The process of separate particles aggregating or coalescing together; concretion; a thing formed in this manner.

The formation of planets, stars, and other celestial bodies by the aggregating of matter drawn together by gravity; also, the growth of a celestial body through this process.

Something gradually added to or growing on a thing externally.

A substance which has built up on the surface of an object, rather than become embedded in it.

Increase in property by the addition of other property to it (for example, gain of land by alluvion (the deposition of sediment by a river or sea) or dereliction (recession of water from the usual watermark), or entitlement to the products of the property such as interest on money); or by the property owner acquiring another person’s ownership rights; accession; an instance of this.

Increase of an inheritance to an heir or legatee due to the share of a co-heir or co-legatee being added to it, because the latter person is legally unable to inherit the share.

Source: wiktionary.org