the world > animals > mammals > group Ungulata (hoofed) > family Equidae (general equines) > habits and actions of horse > [adjective] > leaping or prancing > bucking (3)
Of a horse: That bucks or buck-jumps.
Of a horse or steer: bucking with a violent, twisting motion. Cf. sunfish, v.
Inclined to buck; hence, high-spirited, in good fettle (slang, of persons).