1.Definition: broadly or extravagantly humorous; resembling farce

"Ludicrous green hair"

Related Adjective(s):farcical, ridiculous

2.Definition: so unreasonable as to invite derision

"It is ludicrous to call a cottage a mansion"

Related Adjective(s):absurd, cockeyed, derisory, idiotic, laughable, nonsensical, preposterous, ridiculous