n. A minute particle, molecule, or atom of matter.n. In zoology and anatomy, some small body regarded by itself and characterized by a qualifying term: usually a body of microscopic size; a cell. See phrases below.n. In botany, specifically, one of several large cells within the endosperm and near the summit of the embryo sac in gymnosperms, from which after fertilization an embryo is developed: so named by R. Brown.n. Same as corposant.n. Of the kidney, small globular masses of dark-red color, found in the cortical substance of the organ, consisting of a central glomerulus of blood-vessels (the Malpighian tuft), and of a membranous capsule which is the beginning of a uriniferous tubule.n. In electricity, a body smaller than an atom, assumed to explain the phenomena of electric discharges in gases, and of radioactivity.