Definition of concretion

• n. - The process of concreting; the process of uniting or of becoming united, as particles of matter into a mass; solidification.
• n. - A mass or nodule of solid matter formed by growing together, by congelation, condensation, coagulation, induration, etc.; a clot; a lump; a calculus.
• n. - A rounded mass or nodule produced by an aggregation of the material around a center; as, the calcareous concretions common in beds of clay.