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 White House announced the cuts through a legally nebulous ‘pocket rescission’ just five days before the fiscal year ends. — Andrew J. Campa, Los Angeles Times, 27 Sep. 2026

The barn jacket sits in a wonderful nebulous space between the chore jacket and army jacket. — Irene Richardson, InStyle, 24 Sep. 2026

The young sisters’ upbringing, by a troubled mother, mirrors Darya’s own struggles as a parent on some nebulous medication. — Siddhant Adlakha, Variety, 19 Sep. 2026

Now, to be clear, nightclubs like Basement have a longstanding subjective — and often nebulous — criteria for who gets in, and anyone dorky enough to show up to one wearing Meta glasses almost certainly wouldn’t make the cut anyway. — Frank Landymore, Futurism, 27 Aug. 2026

Word History

Etymology

Latin nebulosus misty, from nebula

First Known Use

1674, in the meaning defined at sense 1

Podcast

Get Word of the Day delivered to your inbox!

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