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- his vacant eyes moved across the crowd of amused onlookers, he slowly mirrored their smiles and finally broke into an uncertain grin at the joke which he obviously did not understand. i felt sick inside as i looked at his dull, vacuous smile,3 -- May (52% in)
vacuous = lacking intelligent thought
There are no more uses of "vacuous" in Flowers for Algernon.
Typical Usage (best examples)