Antonym: sensible. Similar words: virtuous, unctuous, sumptuous, voluptuous, tumultuous, tempestuous, contemptuous, presumptuous. Meaning: ['fætʃʊəs] 
adj. devoid of intelligence.
adj. devoid of intelligence. 31. After his boring speech for over an hour, fatuous speaker waited for applause from the audience.
More similar words: virtuous, unctuous, sumptuous, voluptuous, tumultuous, tempestuous, contemptuous, presumptuous, contemptuously, infatuation, arduous, tenuous, strenuous, assiduous, ambiguous, ingenuous, superfluous, innocuous, deciduous, sensuously, incongruous, continuous, conspicuous, mellifluous, promiscuous, gratuitous, disingenuous, fat, father, fate.