preposterous
1. [ adjective ] completely devoid of wisdom or good sense
Synonyms: ridiculous absurd laughable nonsensical cockeyed idiotic ludicrous derisory
Examples:

"the absurd excuse that the dog ate his homework" "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"

Related terms: foolish
Similar spelling:   preposterously
  propositus
  prepossess
  preposition