fatuously UK /ˈfæt.ju.əs.li/US /ˈfæt͡ʃ.u.əs.li/ adverb1 •With smug stupidity or vacuous silliness; idiotically.Will they, like the fellows, judiciously bear a hand in sweeping the stable, or will they fatuously wait to be themselves swept with a besom of destruction? — 1835 formsmore fatuously · most fatuously