idiotic vs preposterous

idiotic and preposterous both are adjectives.

Word	Noun	Adjective	Verb	Adverb
idiotic	No	Yes	No	No
preposterous	No	Yes	No	No

As adjectives, idiotic and preposterous are synonyms defined as:

Other synonyms of idiotic include absurd, cockeyed, derisory, laughable, ludicrous, nonsensical, ridiculous.

idiotic (adjective)	preposterous (adjective)
so unreasonable as to invite derision	so unreasonable as to invite derision
insanely irresponsible
having a mental age of three to seven years