/ Dictionary / Index F foster brother: Meaning and Definition of Find definitions for: fos'ter broth'er Pronunciation: [key] a boy brought up with another child of different parents. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. fosterage foster care Related Content Daily Word Quiz: deleterious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language