Succus \Suc"cus\, n.; pl. {Succi}. (Med.) The expressed juice of a plant, for medicinal use. {Succus entericus}. [NL., literally, juice of the intestines.] (Physiol.) A fluid secreted in small by certain glands (probably the glands of Lieberk["u]hn) of the small intestines. Its exact action is somewhat doubtful.