stupendous UK /stjuˈpɛndəs/US /stuˈpɛndəs/ adjective2 •Astonishingly great or large; huge; enormous.One cannot appreciate how stupendous the Matterhorn is without seeing it. •Of stunning excellence or degree; marvelous.The renovator created a stupendous new look for our house. formsmore stupendous · most stupendous