thoroughbred

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A purebred or pedigreed animal, especially a horse.
• noun Any of a breed of horses, bred chiefly for racing, originating from crosses between Arabian stallions and English mares.
• noun A well-bred person.
• adjective Bred of pure stock; purebred.
• adjective Relating or belonging to horses of the Thoroughbred.
• adjective Thoroughly trained or educated; well-bred.

from The Century Dictionary.

• Of pure or unmixed breed, stock, or race; bred from a sire and dam of the purest or best blood. See II.
• Hence Having the qualities characteristic of pure breeding; high-spirited; mettlesome; elegant or graceful in form or bearing: sometimes applied colloquially to persons.
• Thoroughgoing; thorough.
• noun An animal, especially a horse, of pure blood, stock, or race; strictly, and as noting horses, a race-horse all of whose ancestors for a given number of generations (seven in England, five in America) are recorded in the stud-book.

from the GNU version of the Collaborative International Dictionary of English.

• adjective Bred from the best blood through a long line; pure-blooded; -- said of stock, as horses. Hence, having the characteristics of such breeding; mettlesome; courageous; of elegant form, or the like.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• adjective bred from pure stock
• adjective well-bred and properly educated
• noun A particular breed of horse (this does not refer to any purebred horse)
• noun A well-bred person.
• noun A person of uncommon strength or endurance.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a well-bred person
• noun a racehorse belonging to a breed that originated from a cross between Arabian stallions and English mares
• noun a pedigreed animal of unmixed lineage; used especially of horses
• adjective having a list of ancestors as proof of being a purebred animal