thoroughbred

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A purebred or pedigreed animal, especially a horse.
2. n. Any of a breed of horses, bred chiefly for racing, originating from a cross between Arabian stallions and English mares.
3. n. A well-bred person.
4. adj. Bred of pure stock; purebred.
5. adj. Relating or belonging to horses of the Thoroughbred.
6. adj. Thoroughly trained or educated; well bred.

Century Dictionary and Cyclopedia

1. Of pure or unmixed breed, stock, or race; bred from a sire and dam of the purest or best blood. See II.
2. Hence Having the qualities characteristic of pure breeding; high-spirited; mettlesome; elegant or graceful in form or bearing: sometimes applied colloquially to persons.
3. Thoroughgoing; thorough.
4. n. 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. In America the name is now loosely given to any animal that is of pure blood and recorded pedigree, or is entitled to be recorded in a stud-book, herd-book, or flock-register, and whose ancestry is known and recorded for five generations of dams and six of sires. In the most restricted sense a thoroughbred is the English race-horse, with ancestry recorded in the stud-book; a pure-bred is a similarly bred animal of another breed, with recorded ancestry in herd-books, stud-books, flock-books, or other pedigree-records. Sometimes applied colloquially to persons.

Wiktionary

1. adj. bred from pure stock
2. adj. well-bred and properly educated
3. n. A particular breed of horse (this does not refer to any purebred horse)
4. n. A well-bred person.
5. n. A person of uncommon strength or endurance.

GNU Webster's 1913

1. adj. 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.

WordNet 3.0

1. n. a well-bred person
2. n. a racehorse belonging to a breed that originated from a cross between Arabian stallions and English mares
3. n. a pedigreed animal of unmixed lineage; used especially of horses
4. adj. having a list of ancestors as proof of being a purebred animal