Diminution (n.) The act of diminishing, or of making or becoming less; state of being diminished; reduction in size, quantity, or degree; -- opposed to augmentation or increase.

Diminution (n.) The act of lessening dignity or consideration, or the state of being deprived of dignity; a lowering in estimation; degradation; abasement.

Diminution (n.) Omission, inaccuracy, or defect in a record.

Diminution (n.) In counterpoint, the imitation of, or reply to, a subject, in notes of half the length or value of those the subject itself.