preposterous

adjective

pre·​pos·​ter·​ous pri-ˈpä-st(ə-)rəs 

: contrary to nature, reason, or common sense : absurd

preposterously adverb

preposterousness noun

Synonyms

• absurd
• bizarre
• crazy
• fanciful
• fantastic
• fantastical
• foolish
• insane
• nonsensical
• unreal
• wild

Examples of preposterous in a Sentence

The whole idea is preposterous!

the idea that extraterrestrials built the pyramids is preposterous

Recent Examples on the Web

The Leafs took four penalties in that period alone — a preposterous amount in a game carrying these kinds of stakes. —Chris Johnston, New York Times, 12 May 2025

The women in Trollope’s work seem to understand how curtailed their lives are, and their behavior—as the pet of their husband or of their father—is calibrated in response to the preposterous conditions of being a woman in the nineteenth century. —The New Yorker, New Yorker, 30 Apr. 2025

That was a fun, if preposterous movie, but it was actually based on the 1975 Japanese thriller Bullet Train. —Erik Kain, Forbes.com, 25 Apr. 2025

In terms of achievements that were once equally preposterous and inconceivable 30 years ago, TCU reaching the Sweet 16 in women’s basketball is on the same level as the school making the national title game in football. —Mac Engel, Fort Worth Star-Telegram, 25 Mar. 2025

Word History

Etymology

Latin praeposterus, literally, in the wrong order, from prae- + posterus hinder, following — more at posterior

First Known Use

1533, in the meaning defined above

Kids Definition

preposterous

adjective

pre·​pos·​ter·​ous pri-ˈpäs-t(ə-)rəs 

: making little or no sense : absurd

preposterously adverb

preposterousness noun

Etymology

from Latin praeposterus, literally, "having the rear part in front," from prae- "in front, before" and posterus "coming behind, following"

Word Origin

The familiar expression "putting the cart before the horse" comes very close to the literal sense of the word preposterous. The Romans formed their Latin adjective praeposterus from prae-, meaning "before," and posterus, meaning "following." They at first used it to mean "having that first which ought to be last," like having a cart ahead of the horse that is pulling it. Praeposterus was used to describe something that was out of the normal or logical order or position. From this developed the more general sense of "ridiculous, absurd." These meanings were borrowed into English in the 16th century. Although preposterous is seldom used in its literal sense nowadays, we still use it to describe something that seems so unreasonable as to be ridiculous.