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 otherworldly—after all, it’s related to nebula, which refers to 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 Teju Cole wrote of an avant-garde photographer who viewed photography as existing “neither in the camera nor in the printed photograph, but in a more nebulous zone.”

Synonyms of nebulous

• ambiguous
• cryptic
• obscure
• dark
• vague

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

Fads come, and fads go, and even small changes in platforms’ nebulous algorithms can drop you off the map overnight. —Corey Buhay, Outside, 26 Feb. 2026

The drama is shot with a documentarian’s eye and unfolds in the ruins of an unnamed city, but its setting is far from nebulous — not least because of the presence of a few Palestinian flags. —Siddhant Adlakha, Variety, 21 Feb. 2026

Plans could blur as the impressionable Moon merges with nebulous Neptune in your 11th House of Friendship and Community, bringing welcome compassion but also frustratingly hazy expectations. —Tarot.com, New York Daily News, 19 Feb. 2026

The gist of the 10 criminal charges against a public servant who has had a sterling record of decades of service on behalf of the city taxpayers as clerk and a commissioner of the Waukegan Park District was nebulous, a county judge and appellate panel have indicated. —Charles Selle, Chicago Tribune, 13 Feb. 2026

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