Of an animal: of excellent breed or stock; of a superior nature, spirit, or disposition. Obsolete.

Of an animal, esp. a horse: of good breed or stock. Obsolete.

Of an animal: of good or pure stock.

of pure breeding (opposed to half-bred, adj. 1); cf. sense A. 9b.

Of a horse: of good or pure stock; well-bred.

Originally: designating an animal bred to a standard, esp. one prescribed by an authority. In later use chiefly: designating a horse of the…