circumstantially adv. + Add to list US //ˌsɝkəmˈstænʃəˌɫi// UK //sˈɜːkəmstˌɑːnʃəlˌi// cir·cum·stan·tial·ly SynonymsAntonymsEtymology Synonyms accidentallyminutelyunexpectedly Antonyms deliberatelyOrigin From circumstantial + -ly.