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If an idea seems nebulous, what is it lacking?

nebulous

American  
[neb-yuh-luhs] / ˈnɛb jə ləs /

adjective

  1. hazy, vague, indistinct, or confused.

    a nebulous recollection of the meeting; a nebulous distinction between pride and conceit.

  2. cloudy or cloudlike.

  3. of or resembling a nebula or nebulae in deep space; nebular.


nebulous British  
/ ˈnɛbjʊləs /

adjective

  1. lacking definite form, shape, or content; vague or amorphous

    nebulous reasons

  2. of, characteristic of, or resembling a nebula

  3. rare misty or hazy

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Other Word Forms


Etymology

Origin of nebulous

First recorded in 1375–1425; late Middle English, from Latin nebulōsus “full of mist, foggy, cloudy,” from nebul(a) “cloud, mist, vapor” ( see nebula) + -ōsus -ous


Explanation

Something that's nebulous is clouded or hazy. When you walk through the woods on a foggy morning, the trees may all have a mysterious, nebulous look to them. When you fly in a plane on an overcast day, the land below you looks nebulous and indistinct. You can also use nebulous in a more figurative way, to describe vague ideas or fuzzy concepts. Nebulous comes from the Latin nebulosus, "cloudy, misty, or foggy." Its root is nebula, which is "vapor or fog" in Latin and was adopted by astronomers in the 1700s to mean "a cloud of gas and dust in outer space."

Keep Reading on Vocabulary.com

Vocabulary lists containing nebulous

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

See Examples For:

A sippable sweet treat: Refreshers—a nebulous class of drinks similar to lemonade or smoothies—are taking over menus from Starbucks to McDonald’s.

From Slate ● Aug. 14, 2026

The average country listener wants to have their past misremembered for them, whether it’s the Judds asking Grandpa about the good old days or Tim McGraw missing the nebulous “back when.”

From Salon ● Aug. 3, 2026

But its route to a return that matches its debt-fueled investments in AI computing power is nebulous at best.

From The Wall Street Journal ● May 5, 2026

"Once again, the nebulous Boko Haram terrorist group carried out a cowardly attack last night on our military base at Barka Tolorom," Chadian President Mahamat Idriss Deby Itno said on Tuesday in a Facebook post.

From Barron's ● May 5, 2026

It had happened that morning at the Ministry, if anything so nebulous could be said to happen.

From "1984" by George Orwell

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