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
• foolish
• unreal
• insane
• fantastical

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

Advertisement Read more: The New Superman Hinges on a Radical Reinvention of the Man of Steel’s Parents Our next big-screen Superman barely survived the preposterous self-seriousness of the stories Zack Snyder built around him in Man of Steel (2013) and Batman vs. Superman (2016). —Stephanie Zacharek, Time, 11 July 2025

The highlight is a flotilla of teens on boats tied together like a seafood smorgasbord, but the preposterous sight of a great white eating a hovering rescue helicopter has a certain je ne sais quoi. —Chris Nashawaty, EW.com, 20 June 2025

Indeed, the support for Iran from Lula and much of Latin America’s old-guard left is preposterous. —Andres Oppenheimer, Miami Herald, 20 June 2025

During his more-than-four-hour closing argument, the attorney dismissed claims that Combs Global (née Combs Enterprises) is a racketeering enterprise, saying the idea is preposterous. —Kevin Dolak, HollywoodReporter, 27 June 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.