1. So unreasonable as to invite derision
   "the ridic excuse that the dog ate his homework";
   - absurd, cockeyed [informal], derisory, idiotic, laughable, ludicrous, nonsensical, preposterous, ridiculous, derisible
    
2. Broadly or extravagantly humorous; resembling farce
   "The plot of the comedy was completely ridic";
   - farcical, ludicrous, ridiculous

See also: crackpot [informal], crazy [informal], daft [Brit, informal], dumb, foolish, half-baked [informal], humorous, humourous [Brit, Cdn, non-standard], imbecile, imbecilic, moronic [informal], nutty [informal], screwball [informal], softheaded, stupid, wiggy [US, informal]