WordWeb Online

1. So unreasonable as to invite derision
   "her conceited assumption of universal interest in her rather dull children was ridiculous";
   - absurd, cockeyed [informal], derisory, idiotic, laughable, ludicrous, nonsensical, preposterous, ridic [informal]
    
2. Broadly or extravagantly humorous; resembling farce
   "the wild ridiculous exuberance of a clown";
   - farcical, ludicrous, ridic [informal]
    
3. Inspiring scornful pity
   "how ridiculous an ardent and unsuccessful wooer can be especially if he is getting on in years";
   - pathetic, silly

See also: daft [Brit, informal], dumb, foolish, humorous, humourous [Brit, Cdn, non-standard], imbecile, imbecilic, stupid, undignified

Encyclopedia: Ridiculous