Next in order or rank after the eighteenth: an ordinal numeral: as, the nineteenth time.Being one of nineteen: as, a nineteenth part.n. A nineteenth part; the quotient of unity divided by nineteen.n. In music, the interval, whether melodic or harmonic, between any tone and a tone two octaves and a fifth distant from it; also, a tone distant by such an interval from a given tone.n. In organ-building, a stop whose pitch is two octaves and a fifth above that of the keys used, as, for example, the larigot.