Definition of accretions:
(n) :
(uncountable, also figurative) 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.
(n) :
(uncountable) (Gradual) increase by an external addition of matter; (countable) an instance of this.
(n) :
(uncountable, also figurative) Followed by of: external addition of matter to a thing which causes it to grow, especially in amount or size.
(n) :
(uncountable) The process of separate particles aggregating or coalescing together; concretion; (countable) a thing formed in this manner.
(n) :
(astrophysics) 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.
(n) :
(countable, chiefly figurative) Something gradually added to or growing on a thing externally.