accretion

ac·cre·tion

noun \ə-ˈkrē-shən\

Definition of ACCRETION

: the process of growth or enlargement; especially : increase by external addition or accumulation (as by adhesion of external parts or particles)—compare apposition 1, intussusception 2

—ac·cre·tion·ary \-shə-ˌner-ē\ adjective