Synonyms of idiotic

1. crackbrained, idiotic, insane (vs. sane): usage: insanely irresponsible; "an idiotic idea"
2. absurd, cockeyed, derisory, idiotic, laughable, ludicrous, nonsensical, preposterous, ridiculous, foolish (vs. wise): usage: incongruous;inviting ridicule; "the absurd excuse that the dog ate his homework"; "that's a cockeyed idea"; "ask a nonsensical question and get a nonsensical answer"; "a contribution so small as to be laughable"; "it is ludicrous to call a cottage a mansion"; "a preposterous attempt to turn back the pages of history"; "her conceited assumption of universal interest in her rather dull children was ridiculous"
3. imbecile, imbecilic, idiotic, retarded (vs. precocious): usage: having a mental age of three to seven years