1. Nebulous \ˈne-byə-ləs\ in the form of a cloud or haze; hazy
Adjective, from the Latin noun nebula: Mist, cloud
in the form of a cloud or haze; hazy
not seen or understood clearly

2. Nebulous: History and related terms
In 17th-Century English, Nebula referred to a speck on the eye that caused vision problems. Later, it was used to label the clouds of gas and dust in outer space where stars form. Here’s the Crab Nebula in the constellation of Taurus
Recognize these Spanish words that share the same root?
nube nublado neblina

3. Synonyms
Ambiguous
Blurry
Indefinite
Murky
Mysterious
Unclear
Vague

4. Antonyms
Apparent
Clear
Definite
Obvious
Plain
Precise

5. In Context
Of course I’d like to complete this assignment, but the instructions are rather nebulous, don’t you think?
She spent hours trying to interpret her nebulous dreams.
The doctor made nebulous references to the runner’s future after the runner had broken his leg.