n. The act of reversing, or of altering a position, direction, action, condition, or state to its opposite or contrary; also, the state of being reversed.n. In physics, specifically, the changing of a bright line in a spectrum, produced by an incandescent vapor, into a dark line (by absorption), and the reverse.n. The act of repealing, revoking, or annulling; a change or overthrowing: as, the reversal of a judgment, which amounts to an official declaration that it is erroneous and rendered void or terminated; the reversal of an attainder or of an outlawry.n. In biology, reversion.Causing, intending, or implying reverse action; reversing.n. In international law: A promise by a sovereign power that a certain order, or certain conditions, promulgated or established, will be observed, notwithstanding changes that may occur to cause deviation therefrom. For instance, when France recognized Russia as an imperial government, a reversal was required that Russia would not cause any derogation from the rank which France had held toward her.n. A declaration by a sovereign that by a given act he means no prejudice to another power.n. In electricity, the process of changing the direction of the current in a circuit. In telegraphy the term is applied to the sending of signals over the line by means of rapidly reversed or alternating currents.