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

But his role within the company long felt awkward because key division managers, including the heads of CBS, the Paramount movie studio and the company’s streaming businesses, reported to Ellison, which left Shell with a nebulous portfolio. —Meg James, Los Angeles Times, 8 Apr. 2026

If justice means anything any more, a federal judge will easily swipe through Hegseth’s nebulous legal fantasies, and preserve the possibility that someday, the Endangered Species Act might actually help save endangered species in the Gulf. —Orlando Sentinel Editorial Board, The Orlando Sentinel, 8 Apr. 2026

The legal conversation is settled, and far more explicit than other consequential decisions in which the court must weigh potentially conflicting precedents and nebulous congressional intent. —New York Daily News Editorial Board, New York Daily News, 1 Apr. 2026

In the days immediately following its mid-January perihelion, its head was described as a diffused nebulous mass, but far more noteworthy was its tail, described as a pale narrow ribbon of light. —Joe Rao, Space.com, 31 Mar. 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