Next after the seventh: an ordinal numeral.n. The quotient of unity divided by eight; one of eight equal parts of anything.n. In music: The interval between any tone and a tone on the eighth diatonic degree above or below it; an octave.n. A tone distant by an eighth or octave from a given tone; an octave or replicate. The eighth tone of a scale is really the prime or key-note of a replicate scale.n. An eighth-note.n. In early English law, an eighth part of the rents for the year, or of movables, or both, granted or levied by way of tax.