/ Dictionary / Index M mother-in-law: Meaning and Definition of Find definitions for: moth•er-in-law Pronunciation: (mu'ur-in-lô"), [key] — pl. moth•ers-in-law. the mother of one's husband or wife. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: mother-in-law (Thesaurus) Mothering Sunday mother-in-law plant Related Content Daily Word Quiz: fresco Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language