CANCER, in Medicine, a roundish, unequal, hard, and livid tumour, generally seated in the glandulous parts of the body, supposed to be so called, because it appears at length with turgid veins shooting out from it, so as to resemble, as it is thought, the figure of a crab-fish, or others say, because, like that fish, where it has once got, it is scarce possible to drive it away. See MEDICINE Index.