What does unthinkable mean?
"Unthinkable" describes an idea, action, or outcome that is so improbable, extreme, or contrary to accepted beliefs that it cannot seriously be imagined. Its force comes from combining a negative prefix with an ordinary act of mental consideration: something is not merely difficult to think about, but outside the range of ideas people can reasonably entertain. The word is often used in formal discussion to dismiss a proposal or describe a formerly inconceivable development. For example, a society in which people regularly communicate through invisible devices may once have seemed unthinkable, but changing circumstances can make even the most extraordinary ideas plausible. As an adjective, "unthinkable" is the standard form; the related adverb "unthinkably" is used especially in expressions such as "unthinkably bad." The phrase "the unthinkable" treats the concept as a noun, referring to something impossible or utterly unacceptable to contemplate.
So unlikely, extreme, or impossible that it cannot reasonably be imagined or considered.
"Such a dramatic change in public behavior would have been unthinkable a generation earlier."
Commonly used with propositions, actions, outcomes, and circumstances. It can be strongly rhetorical, especially when used to dismiss an idea without discussion.
Something so unlikely or impossible that it cannot reasonably be imagined or considered.
"The collapse of the entire system had always been the unthinkable."
Usually used in the singular phrase "the unthinkable" and often carries a rhetorical or dismissive force.
The noun is normally used in the singular phrase "the unthinkable"; plural forms are not standard.
"For the company, abandoning its founding principles had long been the unthinkable."
Unthinkable is more than unlikely: it names the point where an idea leaves the realm of serious consideration altogether.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does unthinkable come from?
"Unthinkable" was formed in the early 17th century from the negative prefix "un-", the verb "think," and the suffix "-able." The verb "think" comes from Old English "þencan," while "-able" is a productive suffix ultimately associated with Latin forms meaning "able to be." The compound was originally understood as "not able to be thought" and developed into a word for what is impossible to imagine or seriously consider.
Related word forms
How unthinkable is actually used
This is a formal and often emphatic word. It is especially useful when discussing a proposal, possibility, or outcome as so implausible that it deserves no serious consideration; in less formal contexts, "impossible" or "inconceivable" may sound more natural.
Easily confused with unthinkable
"Unthinking" means lacking careful thought or consideration, whereas "unthinkable" describes an idea or action that is itself impossible to imagine.