thor·ough·bred (thûrō-brĕd′, thûrə-, thŭr-)
1. A purebred or pedigreed animal, especially a horse.
2. Thoroughbred Any of a breed of horses, bred chiefly for racing, originating from crosses between Arabian stallions and English mares.
3. A well-bred person.
1. Bred of pure stock; purebred.
2. Thoroughbred Relating or belonging to horses of the Thoroughbred.
3. Thoroughly trained or educated; well-bred.
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2020 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.