What is the meaning of idiotic?

adjective

• Insanely irresponsible.
  • usage: "an idiotic idea"
  • synonyms: crackbrained
• Incongruous; inviting ridicule.
  • usage: "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"
  • synonyms: absurd, cockeyed, derisory, laughable, ludicrous, nonsensical, preposterous, ridiculous
• Having a mental age of three to seven years.
  • synonyms: imbecile, imbecilic