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