nebulous

adjective

neb·​u·​lous ˈne-byə-ləs 

1

: of, relating to, or resembling a nebula : nebular

2

: indistinct, vague

… this nebulous thing called jazz.

—Josef Woodard

… the nebulous region between mere suspicion and probable cause

—W. R. LaFave & J. H. Israel

The plan is too nebulous.

nebulously adverb

nebulousness noun

Did you know?

Nebulous may sound other-worldly—after all, it’s related to nebula, which refers to a distant galaxy or an interstellar cloud of gas or dust—but its mysteriousness is rooted in more earthly unknowns. Both words ultimately come from Latin nebula, meaning “mist, cloud,” and as far back as the 14th century nebulous could mean simply “cloudy” or “foggy.” Nebulous has since the late 17th century been the adjective correlating to nebula (as in “nebulous gas”), but the word is more familiar in its figurative use, where it describes things that are indistinct or vague, as when Jack London wrote of “ideas that were nebulous at best and that in reality were remembered sensations.”

Synonyms

• ambiguous
• arcane
• cryptic
• dark
• deep
• Delphic
• double-edged
• elliptical
• elliptic
• enigmatic
• enigmatical
• equivocal
• fuliginous
• inscrutable
• murky
• mysterious
• mystic
• obscure
• occult
• opaque

Examples of nebulous in a Sentence

These philosophical concepts can be nebulous.

made nebulous references to some major changes the future may hold

Recent Examples on the Web

Nadella not being read in on the nebulous details of Stargate says a lot about how much Microsoft and OpenAI have drifted apart. —Alex Heath, The Verge, 25 Jan. 2025

That looks suspicious when other people, including agent Nicole Robinson (Krys Marshall) and nebulous billionaire Samantha Redmond (Nicholson), find out. —Daniel Fienberg, The Hollywood Reporter, 24 Jan. 2025

That statistic makes an abstract, hard-to-substantiate criticism, but then this is a nebulous era at Dortmund, where the belief is no longer in the tactical tenets, but in the culture of the club itself. —Sebastian Stafford-Bloor, The Athletic, 21 Jan. 2025

Kerr praised both Green and Curry’s leadership in regard to their willingness to make changes amid the team’s current slide — Green with his nebulous role and Curry adjusting his traditional substitution pattern. —Danny Emerman, The Mercury News, 8 Dec. 2024

Word History

Etymology

Latin nebulosus misty, from nebula

First Known Use

1674, in the meaning defined at sense 1

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Kids Definition

nebulous

adjective

neb·​u·​lous ˈneb-yə-ləs 

1

: of, relating to, or resembling a nebula

2

: not clear or sharp : vague

nebulously adverb

nebulousness noun