a. [ L. fatuus. ] 1. Feeble in mind; weak; silly; stupid; foolish; fatuitous. Glanvill. [ 1913 Webster ]
2. Without reality; illusory, like the ignis fatuus. [ 1913 Webster ]
Thence fatuous fires and meteors take their birth. Danham. [ 1913 Webster ]
n. a ludicrous folly. Syn. -- absurdity, fatuity, silliness. [ WordNet 1.5 ]