Next in order after the eleventh: an ordinal numeral.Being one of twelve equal parts into which a whole is regarded as divided.n. One of twelve equal parts of anything; the quotient of unity divided by twelve.n. In early English law, a twelfth of the rents of the year, or of movables, or both, granted or levied by way of tax.n. In music, a tone twelve diatonic degrees above or below a given tone, or the interval between two such tones; a compound fifth.n. In organ-building, a stop giving tones a twelfth above the normal pitch of the digitals used.n. Twelfth-day.