(n) skin tumor that grows rapidly (especially in older people) and resembles a carcinoma but does not spread; it usually disappears spontaneously, often leaving a scar
n. [ Gr. ke`ras, -atos, horn. ] (Physiol. Chem.) A sulfur-containing fibrous protein constituting the main structural protein of hard epidermal tissues, such as horn, hair, feathers, nails, claws, hoofs, and the like. It is an insoluble substance, and, unlike elastin, is not dissolved even by gastric or pancreatic juice. By decomposition with sulphuric acid it yields leucine and tyrosine plus various other acid-stable amino acids. The amino acid composition varies, but it usually has a high percentage of cystine, which stabilizes and insolubilizes the protein by forming intrachain linkages. A softer form of keratin is present in the epidermis and whalebone. Called also epidermose. [ 1913 Webster +PJC ]
‖n. [ Gr. ke`ras, -atos, horn + &unr_; puncture. ] (Med.) The operation of removing a cataract by thrusting a needle through the cornea of the eye, and breaking up the opaque mass. [ 1913 Webster ]
‖n. pl. [ NL., fr. Gr. ke`ras, -atos, a horn. ] (Zool.) An order of sponges having a skeleton composed of hornlike fibers. It includes the commercial sponges. [ 1913 Webster ]
n. [ Gr. ke`ras, -atos, horn. ] (Physiol. Chem.) A tough, horny animal substance entering into the composition of the skeleton of sponges, and other invertebrates; -- called also keratode. [ 1913 Webster ]