starfish

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. Any of various marine echinoderms of the class Asteroidea, characteristically having a thick, often spiny body with five arms extending from a central disk. Also called asteroid, sea star.

Century Dictionary and Cyclopedia

1. n. An echinoderm with five or more arms radiating from a central disk: applied to all the members of the Asteroidea and Ophiuroidea (see these words). These belong to the phylum Echinodermata, which contains also the sea-urchins, holothurians, crinoids, etc., though these are not usually called starfishes. In some of the asteroids or starfishes proper the disk is enlarged so as to take in nearly or quite the whole length of the rays, so that the resulting figure is a pentagon, or even a circle; but in such cases the stellate structure is evident on examination. Such are known as cushion-stars. In the ophiurians the reverse extreme occurs, the body being reduced to a small circular central disk, with extremely long slender rays, which in some, as the eury-aleans, are branched into several thousand ramifications. (See cut under basket-fish.) The commonest type of starfish has five rays; whence such are popularly known as five-fingered jack or fivefingers. (See cuts under Asterias and Echinaster.) Those with more than five rays are often called sun-starfish or sun-stars. (See Heliaster, and cuts under Brisinga and Solaster.) The skin of starfishes is tough and leathery, and usually indurated with calcareous plates, tubercles, spines, etc. It is so brittle that starfishes readily break to pieces, sometimes shivering like glass into many fragments. This fragility is at an extreme in the ophiurians, sometimes, on this account, called brittle-stars. (See cut under Astrophyton.) Lost arms are readily replaced by a new growth, if the body of the starfish is not broken. On the under side of the animal's rays may be observed rows of small holes; these are the ambulacra, through which protrude many small soft, fleshy processes—the pedicels, tube-feet, or ambulacral feet—by means of which the creatures crawl about. The ambulacra converge to a central point on the under side, where is the oral opening or mouth. The animals are extremely voracious, and do great damage to oyster-beds. They abound in all seas at various depths, and some of them are familiar objects on every sea-coast. Some of the free crinoids of stellate figure are included under the name starfishes, though they are usually called lily-stars or feather-stars. Encrinites are fossil starfishes of this kind. (See cuts under Comatulidæ and encrinite.) Very different as are the appearances superficially presented by a starfish, a sea-urchin, a holothurian, and a crinoid, their fundamental unity of structure may be easily shown. If, for instance, a common five-fingered jack should have its arms bent up over its back till they came to a center opposite the mouth, and then soldered together in that position by plates filling the spaces between the arms, it would make the globular or oblate spheroid figure of a sea-urchin. If a starfish should turn over on its back, and have a stem grow from the center, and then have its arms come together like the petals of a lily, it would represent a crinoid. If, again, the starfish should have its arms reduced to mere rudiments, or to tentacular appendages of an elongated leathery body, it would represent a holothurian, sea-slug, or trepang. These are the principal types of echinoderms—in fact less unlike one another than are the several stages they uudergo in development, for which see Asteroidea, Bipinnaria, Brachiolaria, echinopædium, and pluteus.
2. n. The butter-fish or dollar-fish.
3. n. In heraldry, a bearing representing a five-pointed star, the rays surrounded by short waving flames or the like, and having a small circle in the center.

Wiktionary

1. n. Any of various asteroids or other echinoderms (not in fact fish) with usually five arms, many of which eat bivalves or corals by everting their stomach.
2. n. vulgar, slang, usually in translations of Japanese pornography an anus. See also chocolate starfish.
3. n. obsolete Any many-armed or tentacled sea invertebrate, whether cnidarian, echinoderm, or cephalopod.

GNU Webster's 1913

1. n. (Zoöl.) Any one of numerous species of echinoderms belonging to the class Asterioidea, in which the body is star-shaped and usually has five rays, though the number of rays varies from five to forty or more. The rays are often long, but are sometimes so short as to appear only as angles to the disklike body. Called also sea star, five-finger, and stellerid.
2. n. (Zoöl.) The dollar fish, or butterfish.

WordNet 3.0

1. n. echinoderms characterized by five arms extending from a central disk