asteroid

1 of 2

noun

as·​ter·​oid ˈa-stə-ˌrȯid 

1

: any of the small rocky celestial bodies found especially between the orbits of Mars and Jupiter

2

: starfish

asteroidal

ˌa-stə-ˈrȯi-dᵊl 

adjective

asteroid

2 of 2

adjective

1

: resembling a star

asteroid bodies in sporotrichosis

2

: of or resembling a starfish

Examples of asteroid in a Sentence

Noun

Most asteroids are found between Mars and Jupiter.

Recent Examples on the Web

Noun

Psyche is a nickel-iron core asteroid that orbits the sun beyond Mars anywhere from 235 million to 309 million miles away. —Richard Tribou, The Orlando Sentinel, 25 June 2025

Later in 2025, the Rubin Observatory will begin the Legacy Survey of Space and Time (LSST), which is expected to detect 90% of all potentially hazardous asteroids over 140 meters wide, as well as rogue planets, interstellar comets, and supernovae — exploding stars. —Jamie Carter, Forbes.com, 23 June 2025

Adjective

Venus: Asteroids around Venus pose possible 'invisible threat' to Earth What is asteroid 2024 YR4? —Eric Lagatta, USA Today, 10 June 2025

What is asteroid 2024 YR4 and why are scientists paying attention to it? —Eric Lagatta, USA TODAY, 13 Feb. 2025

Word History

Etymology

Noun

Greek aster-, astḗr "star" + -oid entry 1, probably after Greek asteroeidḗs "starlike, starry"; (sense 2) after New Latin Asteroidea, class name — more at star entry 1

Note: The first use in print of asteroid in its current sense was by the astronomer William herschel, in the paper "Observations on the two lately discovered celestial Bodies," "Read May 6, 1802" (Philosophical Transactions of the Royal Society of London, for the year MDCCCII, part II [1802], p. 228-29): "With this intention, therefore, I have endeavoured to find out a leading feature in the character of these new stars; and, as planets are distinguished from the fixed stars by their visible change of situation in the zodiac, and comets by their remarkable comas, so the quality in which these objects differ considerably from the two former species, is that they resemble small stars so much as hardly to be distinguished from them, even by very good telescope …From this, their asteroidical appearance, if I may use that expression, therefore, I shall take my name, and call them Asteroids; reserving to myself, however, the liberty of changing that name, if another, more expressive of their nature, should occur." The coinage and reception of this word have been examined in exhaustive detail by Clifford J. Cunningham in "Discovery of the origin of the word asteroid and the related terms asteroidal, planetoid, planetkin, planetule and cometoid," Studia Etymologica Cracoviensia, vol. 20 (2015), pp. 47-62. Cunningham establishes that the word asteroid was suggested by the classicist Charles Burney (1757-1817), through the mediation of his father, the musician and composer Charles Burney (1726-1814), a close friend of William Herschel. Left unanswered, however, and probably unaswerable, is the question of how Burney came upon the word: did he derive it himself, from Greek astḗr "star" and the English suffix -oid, already somewhat productive, or did he consult a Greek dictionary? Note that Greek asteroeidḗs (glossed "sternartig"= "starlike"), not a well-attested word, is entered in Johann Gottlob Schneider's Kritisches griechisch-deutsches Handwörterbuch (Züllichau/Leipzig, 1797), probably the most comprehensive dictionary that would have been available to Burney. As is clear from Herschel's words, the choice of asteroid was determined by their visual resemblance to stars, however inappropriate it might seem to twenty-first century astronomy. Cunningham points out that planetoid—a better descriptive term, as an asteroid resembles a planet more than a star—was actually used (as Italian and French planetoides) by Giuseppe Piazzi, who spotted Ceres, the first asteroid to be discovered. Independently of Piazzi, planetoid was also arrived at by Henry Brougham, editor of the Edinburgh Review, who acidly criticized Herschel's choice of asteroid: "Why not, for instance, call them Concentric Comets, or Planetary Comets, or Cometary Planets? Or, if a single term must be found, why may we not coin such a phrase as Planetoid or Cometoid?" (Edinburgh Review, January, 1803, p. 430). Whatever its defects, the term asteroid has nonetheless become thoroughly established in astronomy.

Adjective

borrowed from Greek asteroeidḗs "starlike, starry," from aster-, astḗr "star, the plant Aster amellus, starfish" + -oeidēs -oid entry 2 — more at star entry 1

First Known Use

Noun

1802, in the meaning defined at sense 1

Adjective

1824, in the meaning defined at sense 1

Phrases Containing asteroid

• asteroid belt

Rhymes for asteroid

• adenoid
• alkaloid
• amoeboid
• amyloid
• aneroid
• anthropoid
• arachnoid
• benzenoid
• carcinoid
• celluloid
• coronoid
• humanoid

Kids Definition

asteroid

noun

as·​ter·​oid

ˈas-tə-ˌrȯid

: one of thousands of small rocky bodies between Mars and Jupiter with diameters from a fraction of a kilometer to nearly 800 kilometers

Medical Definition

asteroid

adjective

as·​ter·​oid ˈas-tə-ˌrȯid 

: resembling a star