Synonyms for affirm Found 11 synonyms across 2 meanings for “affirm”. establish or strengthen as with new evidence or facts (verb) confirmcorroboratesustainsubstantiatesupport to declare or affirm solemnly and formally as true (verb) verifyassertavowaverswanswear Explore Related Words Rhymes with affirmSynonyms for confirmSynonyms for corroborateSynonyms for sustainSynonyms for substantiateSynonyms for support Synonym Finder | Rhyme Finder | Poetry Editor