(Zool.) An amphibious rodent, of the genus Castor. Note: It has palmated hind feet, and a broad, flat tail. It is remarkable for its ingenuity in constructing its lodges or "houses," and dams across streams. It is valued for its fur, and for the material called castor, obtained from two small bags in the groin of the animal. The European species is Castor fiber, and the American is generally considered a variety of this, although sometimes called Castor Canadensis.