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 the term denotes highly advanced artificial intelligence that could surpass human thought, not the category of AI — an already nebulous term — as a whole. — Adi Robertson, The Verge, 9 Oct. 2026

Our children need to be prepared for life and not filled with nebulous theories of fairness and diversity. — Sun Sentinel Editorial Board, Sun Sentinel, 8 Oct. 2026

The administration’s efforts, led by Vice President JD Vance, have sometimes been overestimated or nebulous. — Ana Ceballos, Los Angeles Times, 6 Oct. 2026

Unlike cornrows or two-strand twists, which have clear, specific definitions, goddess braids are more nebulous. — Eden Stuart, Allure, 6 Oct. 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