n. In botany and zoology, a subdivision of an order; a group subordinate to an order; a superfamily. See family, 6, and order, n., 5.n. In architecture, a subordinate or secondary order; an order introduced for decoration, or chiefly so, as distinguished from a main order of the structure.n. In petrography, in the quantitative classification of igneous rocks (see rock), a division lower than order and higher than rang.