English Reference

Word

asteroid

Phoneticsas·ter·oid

US/ˈæstɝˌɔɪd/

UK/ˈɑːstəɹˌɔɪd/

Definitions

01space rock

B2 · Science

n. a large piece of rock or metal that moves around the sun, mostly in the space between Mars and Jupiter.

n. a small rocky or metallic body orbiting the sun, typically found in the asteroid belt between Mars and Jupiter.

“Scientists are tracking a large asteroid that will pass close to Earth next month.”

“The mission aimed to land a probe on the asteroid's surface to analyse its mineral composition and determine its origin within the early solar system.”

Synonyms

planetoidminor planet

02starfish

C2 · Science

n. a sea animal with a flat, star-shaped body and five or more arms.

n. any echinoderm of the class Asteroidea, characterised by a flattened body and radiating arms.

“The diver found a bright red asteroid clinging to the side of the coral reef.”

“Marine biologists observed the asteroid using its tube feet to pry open the shell of a bivalve during the feeding cycle.”

Technical

Usage

In modern general English, 'starfish' or 'sea star' is almost always preferred over 'asteroid'.

Synonyms

starfishsea star

Real-World Examples

“Hera is currently traveling toward its main destination, the asteroid moon Dimorphos.”
ScienceDaily · 26 Aug 2026
“I recently rewatched Armageddon, complete with Bruce Willis, oil drillers sent into space, and an asteroid the size of Texas racing toward Earth.”
ScienceDaily · 7 Aug 2026

Etymology

From aster + -oid, lit. "star-like". Coined by William Herschel.

Borrowed from Ancient Greek ἀστεροειδής (asteroeidḗs), from ἀστήρ (astḗr, “star”) + εἶδος (eîdos, “form”). Analyzable as aster- + -oid. Piecewise doublet of etymology 1. Compare also the botanical taxon Asteroideae.

Etymology adapted from Wiktionary, available under CC BY-SA 4.0.

Related words

Domains

AstronomyZoology

This entry

Level
B2 · Upper Intermediate
Frequency
Frequent
Updated

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English Reference