直肠
Rectum \Rec"tum\ (-t?m), n. [NL. (sc. intestinum), fr. L. rectus straight. See {Right}.] (Anat.) The terminal part of the large intestine; -- so named because supposed by the old anatomists to be straight. See Illust. under {Digestive}.
rectum n : the terminal section of the alimentary canal; from the sigmoid flexure to the anus [also: {recta} (pl)]