The present indicative plural of the substantive verb to be. See be.n. In the metric system, a unit of superficial or square measure, containing 100 square meters, or 119.6 square yards. Its abbreviation is adjectiven. The note immediately above the tonic, ut, in the grave hexachord of Guido d'Arezzo's musical scale.n. A suffix applied to the names of orders in the quantitative classification of igneous rocks proposed by Cross, Iddings, Pirsson, and Washington: as, canadare, columbare. See classification of igneous rocks, under rock.