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

The splashing water captured by the camera is abstracted into a nebulous fog that dissolves the profile of a Parisian bridge in the background. —Erika Landström, Artforum, 2 June 2026

Astrology, a pursuit that hovers in the nebulous space between science and storytelling, is not exactly a robust academic field, and LaFaive had no scholarly studies of Goodman’s life or work to consult. —Rachel Syme, New Yorker, 1 June 2026

The current most popular movie on Netflix is a true-crime documentary exploring an incident that might not even be a crime, and behaviors more nebulous than the law was ever prepared to adjudicate. —Monica Hesse, Washington Post, 31 May 2026

The Boys Mexico has always seemed a bit nebulous with no real details, but the fact that Diego Luna and Gael García Bernal are involved is very reassuring. —Paul Tassi, Forbes.com, 28 May 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