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The posterior portion of the digestive tract in vertebrates and certain invertebrates.
1. (Zoology) the part of the vertebrate digestive tract comprising the colon and rectum
2. (Zoology) the posterior part of the digestive tract of arthropods
a. the last portion of the vertebrate alimentary canal, between the cecum and the anus.
b. the posterior part of the digestive tract of arthropods.
2. the posterior part of the embryonic vertebrate alimentary canal, from which the colon develops. Compare foregut, midgut.