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asteroid Line breaks: as¦ter|oid
Pronunciation: /ˈastərɔɪd/

Definition of asteroid in English:


1A small rocky body orbiting the sun. Large numbers of these, ranging enormously in size, are found between the orbits of Mars and Jupiter, though some have more eccentric orbits.
Example sentences
  • Ceres was initially considered to be a planet until other asteroids with similar orbits were found.
  • Most of the known asteroids orbit the sun in a belt between Mars and Jupiter.
  • These scientists also study the natural satellites of other planets as well as asteroids and comets.
2 Zoology An echinoderm of the class Asteroidea, which comprises the starfishes.
Example sentences
  • The asteroid is preserved with the dorsal surface exposed.
  • Available morphological data suggest no ecologic parameters that would be unusual among living asteroids.
  • An unpaired commonly enlarged interbrachial ossicle, the axillary, occurs in most Paleozoic asteroids, including those treated here.


Zoology Back to top  
Relating to or denoting echinoderms of the class Asteroidea.


Pronunciation: /astəˈrɔɪd(ə)l/
Example sentences
  • The Hubble Space Telescope captured a picture of starlit asteroidal and cometary debris encircling the yellow dwarf star HD 107146.
  • These satellites range in size from small on the asteroidal scales, to nearly as large as Saturn's moon Mimas.
  • Our understanding of astronomy has shown us that cometary and asteroidal impacts are relatively commonplace over timescales of hundreds of millions of years.


Early 19th century: from Greek asteroeidēs 'starlike', from astēr 'star'.

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