nebula

[neb-yuh-luh]
noun, plural nebulae [neb-yuh-lee, -lahy] , nebulas.
1.
Astronomy.
a.
Also called diffuse nebula. a cloud of interstellar gas and dust. Compare dark nebula, emission nebula, reflection nebula.
b.
(formerly) any celestial object that appears nebulous, hazy, or fuzzy, and extended in a telescope view.
2.
Pathology.
a.
a faint opacity in the cornea.
b.
cloudiness in the urine.
3.
any liquid medication prepared for use as a spray.

Origin:
1655–65; < Latin: a mist, vapor, cloud; akin to Greek nephélē cloud, German Nebel fog, haze

nebular, adjective
nonnebular, adjective
prenebular, adjective
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World English Dictionary
nebula (ˈnɛbjʊlə)
 
n , pl -lae, -las
1.  astronomy Compare planetary nebula a diffuse cloud of particles and gases (mainly hydrogen) that is visible either as a hazy patch of light (either an emission or a reflection nebula) or an irregular dark region against a brighter background (dark nebula)
2.  pathol
 a.  opacity of the cornea
 b.  cloudiness of the urine
3.  any substance for use in an atomizer spray
 
[C17: from Latin: mist, cloud; related to Greek nephétē cloud, Old High German nebul cloud, Old Norse njól night]
 
'nebular
 
adj

Collins English Dictionary - Complete & Unabridged 10th Edition
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Etymonline
Word Origin & History

nebula
c.1420, nebule "a cloud, mist," from L. nebula "mist," from PIE *nebh- "cloud, vapor, fog, moist, sky" (cf. Skt. nabhas- "vapor, cloud, mists, fog, sky;" Gk. nephele, nephos "cloud;" Ger. nebel "fog;" O.E. nifol "dark;" Welsh niwl "cloud, fog;" Slav. nebo). Re-borrowed from L. 1661 in sense of "cataracts
in the eye;" astronomical meaning "cloud-like patch in the night sky" first recorded c.1730. As early as Hershel (1802) astronomers realized that some nebulae were star clusters, but distinction of gas clouds from distant galaxies was not made until c.1930.
Online Etymology Dictionary, © 2010 Douglas Harper
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American Heritage
Medical Dictionary

nebula neb·u·la (něb'yə-lə)
n. pl. neb·u·las or neb·u·lae (-lē')

  1. A faint, foglike opacity of the cornea.

  2. A class of oily preparations for use in a nebulizer.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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American Heritage
Science Dictionary
nebula   (něb'yə-lə)  Pronunciation Key 
Plural nebulae (něb'yə-lē') or nebulas
A visible, thinly spread cloud of interstellar gas and dust. Some nebulae are the remnants of a supernova explosion, others are gravity-induced condensations of the gases in the interstellar medium which in certain cases may become a site for the formation of new stars. The term was formerly used of any hazy, seemingly cloudlike object, including what are now recognized as other galaxies beyond the Milky Way; it is restricted now to actual clouds of gas and dust within our own galaxy. ◇ Nebulae are generally classified as bright or dark. Among the bright nebulae are cold clouds that reflect light from nearby stars (reflection nebulae) and hot, ionized clouds that glow with their own light (emission nebulae). Dark nebulae—cold clouds that absorb the passing light from background stars—are called absorption nebulae. See more at star.
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Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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American Heritage
Cultural Dictionary
nebula [(neb-yuh-luh)]

plur. nebulae

In astronomy, a hazy patch of light visible in the sky. Some nebulae are clouds of gas within the Milky Way; others are distant galaxies. (See photo, next page.)

The American Heritage® New Dictionary of Cultural Literacy, Third Edition
Copyright © 2005 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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Example sentences
But in fact planetary nebulae have nothing to do with planets-they are luminous
  clouds thrown off by dying stars.
The gas circles through space in cosmic dust clouds called nebulae.
Planetary nebulae actually have little to do with planets.
Despite their name, planetary nebulae are actually the remains of dead sunlike
  stars.
Synonyms
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