To lessen; make or seem to make less or smaller by any means; reduce: opposed to increase and augment: as, to diminish a number by subtraction; to diminish the revenue by reducing the customs.To lower in power, importance, or estimation; degrade; belittle; detract from.To take away; subtract: with from, and applied to the object removed.In music, to lessen by a semitone, as an interval.To lessen; become or appear less or smaller; dwindle: as, the prospect of success is diminishing by delay.Synonyms Dwindle, Contract, etc. (see decrease); to shrink, subside, abate, ebb, fall off.To taper, as a column.