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

• ambiguous
• cryptic
• obscure
• dark
• vague
• mysterious

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

What makes the Butterfly Star so striking are the two luminous wings of nebulous gas and dust that appear on either side of the disk. —Rupendra Brahambhatt, Interesting Engineering, 30 Aug. 2025

What does that nebulous phrase mean? —Eli Amdur, Forbes.com, 22 Aug. 2025

Personality is a notoriously nebulous concept, fraught with hidden layers. —Webb Wright, Scientific American, 18 Aug. 2025

Yet the actual start of the festivities has long been more nebulous to pinpoint given the constantly growing number of events vying for attention in the days prior. —Viju Mathew, Robb Report, 14 Aug. 2025

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