Next after the fourteenth: an ordinal numeral.n. The quotient of unity divided by fifteen; one of fifteen equal parts of anything: as, eleven fifteenths of an acre.n. In music, the interval or the concord of a double octave.n. In organ-building, a stop whose pipes are tuned two octaves above the keys struck.n. In early English law, a fifteenth part of the rents of the year, or of movables, or both, granted or levied by way of tax. When a fifteenth was the rate for the counties at large, that for towns and demesnes was usually a tenth.