preposterous

Contrary to nature, reason, or common sense; absurd. synonym: foolish.

Having that last which ought to be first; reversed in order or arrangement; inverted.

Contrary to nature, reason, or common sense; irrational; glaringly absurd; nonsensical.

Foolish; ridiculous; stupid; absurd.

Synonyms and Silly, Foolish, etc. (see absurd), monstrous, crazy, mad, wild, ludicrous. See foolish.