1. Astronomy Any of numerous small solar system bodies that revolve around the sun, with orbits lying chiefly between Mars and Jupiter and characteristic diameters roughly between one and several hundred kilometers. Also called minor planet, planetoid.
2. Zoology See starfish.
adj. also as·ter·oi·dal (ăs′tə-roidl)
[From Greek asteroeidēs, starlike : astēr, star; see ster-3 in the Appendix of Indo-European roots + -oeidēs, -oid.]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2019 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.