in·vert • v. / inˈvərt/ [tr.] put upside down or in the opposite position, order, or arrangement: invert the mousse onto a serving plate. ∎ Mus. modify (a phrase) by reversing the direction of pitch changes. ∎ Mus. alter (an interval or triad) by changing the relative position of the notes in it. ∎ chiefly Math. subject to inversion; transform into its inverse. • n. / ˈinvərt/ 1. an arch constructed in an upside-down position to provide lateral support, e.g., in a tunnel. ∎ the concave lower surface of a sewer or drain. 2. dated Psychol. a person showing sexual inversion; a homosexual. 3. Philately a postage stamp printed with an error such that part of its design is upside down. DERIVATIVES: in·vert·i·bil·i·ty / inˌvərtəˈbilitē/ n. in·vert·i·ble adj.