What does preposterous mean?
Preposterous is an adjective describing something so unreasonable or absurd that it provokes ridicule or disbelief. It is stronger than words such as “unusual” or “implausible,” because it implies that the subject plainly contradicts ordinary expectations, logic, or evidence. The word can characterize an idea, claim, plan, action, or situation, as in “a preposterous accusation” or “a preposterous response.” It is used in both formal discussion and everyday speech, although its strong tone makes it unsuitable when neutrality is required. Preposterous has an interesting history: it developed from a word describing something placed in reverse order, and its modern sense reflects the idea of a situation so absurd that it appears to have been turned upside down. Learning the word therefore gives access not only to a forceful criticism but also to a useful example of how a technical historical meaning can become figurative.
adjectiveSo completely unreasonable or absurd that it is ridiculous. The word conveys strong disapproval or disbelief, especially of an idea, claim, action, or situation.
- So unreasonable, absurd, or ridiculous as to be laughable or intolerable.
"The idea that the entire building was designed by a committee is plainly preposterous."
"The proposed solution would require an entirely preposterous reinterpretation of the evidence."
"Critics dismissed the allegation as preposterous, noting that no credible witness supported it."
Preposterous originally meant “in a reversed order,” before developing its modern sense of something so ridiculous that it seems upside down.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does preposterous come from?
The word entered English in the early 17th century, probably through Latin praeposterus, meaning “reversed” or “in a wrong order.” Latin praeposterus combined prae-, meaning “before,” with posterus, meaning “coming after,” and the adjective’s modern sense of “absurd” developed by extension from the idea of something inverted or contrary to nature. The same Latin root is reflected in English words such as posterior, posthumous, and postpone.
Related word forms
How preposterous is actually used
The adjective is strongly evaluative and is common in formal and informal contexts. It is generally more emphatic than “unreasonable” and often suggests that something is not merely mistaken but plainly absurd.
Easily confused with preposterous
No distinct meaning difference is required; the word may be confused with other words such as absurd or ridiculous, which are generally less emphatic.