Definition of asteroid in US English:

asteroid

noun

  • 1A small rocky body orbiting the sun. Large numbers of these, ranging in size from nearly 600 miles (1,000 km) across (Ceres) to dust particles, are found (as the asteroid belt) especially between the orbits of Mars and Jupiter, though some have more eccentric orbits, and a few pass close to the earth or enter the atmosphere as meteors.

    • ‘Our knowledge of comets and asteroids has dramatically improved over the last 20 years.’
    • ‘Some explanations for extinctions and evolution include strikes by asteroids or comets.’
    • ‘Amateur astronomers have made many asteroid, comet, and supernova discoveries.’
    • ‘Most of the known asteroids orbit the sun in a belt between Mars and Jupiter.’
    • ‘Dinosaurs may not have been killed off by asteroid impact dust blocking out sunlight, a geologist says.’
    • ‘When the asteroid hit, it was vaporized by the extreme energy of the impact.’
    • ‘Our star system is chock full of asteroids and comets, in every conceivable orbit and location.’
    • ‘Comets and asteroids also contribute to the near-Earth space environment.’
    • ‘Once an asteroid drifts into either of those regions, it's hard for it to get out.’
    • ‘Both comets and asteroids are the left-over building blocks of the planets in our solar system.’
    • ‘It's just that you can't keep quiet about things like asteroid impacts.’
    • ‘We know very little about these families of asteroids following the same orbit.’
    • ‘Most of the larger asteroids and comets are also in stable orbits around the sun.’
    • ‘In many ways asteroids and comets are likely to offer more varied and abundant natural resources than the Moon.’
    • ‘These glaciers are spotted with craters caused by asteroid impacts.’
    • ‘Ceres was initially considered to be a planet until other asteroids with similar orbits were found.’
    • ‘In our own solar system, asteroids have collided with Earth, the moon and other planets.’
    • ‘There may be other families of small asteroids within our solar system that, even now, remain to be discovered.’
    • ‘You can also get asteroid hazard warnings and geomagnetic storm outlooks.’
    • ‘These scientists also study the natural satellites of other planets as well as asteroids and comets.’
    • ‘So to neglect the problem means that we are vulnerable to asteroid collisions.’
    • ‘It has been suggested that impacts with comets and asteroids provided Earth with much of its water.’
    • ‘Fragments of asteroids and comets pervade interplanetary space.’
    celestial body, heavenly body, sun
    View synonyms
  • 2Zoology
    An echinoderm of the class Asteroidea, which comprises the starfishes.

    • ‘The fossil record is a potential source of needed data, although fossil asteroids are rare, and they tend to be poorly preserved.’
    • ‘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.’
    • ‘Both approaches will shed light on the adaptive significance and functional morphology of asteroids.’

adjective

Zoology
  • Relating to or denoting echinoderms of the class Asteroidea.

Origin

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

Pronunciation

asteroid

/ˈæstəˌrɔɪd//ˈastəˌroid/