1. Having that first which ought to be last; inverted in order.
2. Contrary to nature or reason; not adapted to the end; utterly and glaringly foolish; unreasonably absurd; perverted.
Synonym: absurd, perverted, wrong, irrational, foolish, monstrous.
Origin: L. Praeposterus; prae = before _ posterus coming after, latter. See Posterior.