Emily Dickinson Lexicon

UM'PIRE, n. [Norm. impere; L. imperium, contracted, as in empire.]

1. A third person called in to decide a controversy or question submitted to arbitrators, when the arbitrators do not agree in opinion.
2. A person to whose sole decision a controversy or question, between parties is referred. Thus the emperor of Russia was constituted umpire between Great Britain and the United States, to decide the controversy respecting the slaves carried from the states by the British troops.