Zi Collection, Upper Volume, Page 50, Entry 03 Pronounced sou (falling tone) A large horse in a foreign land. Also, "to shake the reins of a horse, letting it gallop" — Jiyun (Jiyun). Same as the character "bì" (bì). Also, "to shake the reins of a horse, letting it gallop" — Jiyun (Jiyun). Pronounced sou (falling tone) Same meaning.