the world > animals > mammals > group Ungulata (hoofed) > family Equidae (general equines) > horse defined by purpose used for > [adjective] > of form or qualities of race-horse (2)
Of a horse: Characterized by endurance or staying power: contrasted with speedy. Hence stout blood.
In predicative use, chiefly of persons. U.S. Of a race-horse, not in top form. Also in attributive use.