AskDefine | Define jaw

Dictionary Definition



1 the part of the skull of a vertebrate that frames the mouth and holds the teeth
2 the bones of the skull that frame the mouth and serve to open it; the bones that hold the teeth
3 holding device consisting of one or both of the opposing parts of a tool that close to hold an object [syn: jaws]


1 talk socially without exchanging too much information; "the men were sitting in the cafe and shooting the breeze" [syn: chew the fat, shoot the breeze, chat, confabulate, confab, chitchat, chatter, chaffer, natter, gossip, claver, visit]
2 talk incessantly and tiresomely [syn: yack, yack away, rattle on, yap away]
3 chew (food); "He jawed his bubble gum"; "Chew your food and don't swallow it!"; "The cows were masticating the grass" [syn: chew, masticate, manducate]
4 censure severely or angrily; "The mother scolded the child for entering a stranger's car"; "The deputy ragged the Prime Minister"; "The customer dressed down the waiter for bringing cold soup" [syn: call on the carpet, rebuke, rag, trounce, reproof, lecture, reprimand, dress down, call down, scold, chide, berate, bawl out, remonstrate, chew out, chew up, have words, lambaste, lambast]

User Contributed Dictionary



Origin uncertain. Perhaps representing unattested Old English *cēowe ( = German Keu, Dutch kieuw), related to chew.


  • , /ʤɔː/, /dZO:/


  1. One of the bones, usually bearing teeth, which form the framework of the mouth.
  2. The bone itself with the teeth and covering.
  3. Anything resembling the jaw of an animal in form or action; especially plural, the mouth or way of entrance; as, the jaws of a pass; the jaws of darkness; the jaws of death.
  4. A notch or opening.
  5. A notched or forked part, adapted for holding an object in place; as, the jaw of a railway-car pedestal. See Axle guard.
  6. One of a pair of opposing parts which are movable towards or from each other, for grasping or crushing anything between them, as, the jaws of a vise, or the jaws of a stone-crushing machine.
  7. The inner end of a boom or gaff, hollowed in a half circle so as to move freely on a mast.
  8. Impudent or abusive talk.
  9. Axle guard.


bone of the jaw
  • Greek: σαγόνι
  • Latin: maxilla
  • Portuguese: mandíbula
  • Spanish: mandíbula

See also


  1. To assail or abuse by scolding.
  2. To scold; to clamor.

Extensive Definition

The jaw is either of the two opposable structures forming, or near the entrance to the mouth.
The term jaws is also broadly applied to the whole of the structures constituting the vault of the mouth and serving to open and close it and is part of the body plan of most animals.


In arthropods, the jaws are chitinous and oppose laterally, and may consist of mandibles, chelicerae, or loosely, pedipalps.
Their function is fundamentally for food acquisition, conveyance to the mouth, and/or initial processing (mastication or chewing).


In most vertebrates, the jaws are bony or cartilaginous and oppose vertically, comprising an upper jaw and a lower jaw.

Bones of the jaw

In vertebrates, the lower jaw, dentary or mandible is the mobile component that articulates at its posterior processes, or rami (singular ramus), with the temporal bones of the skull on either side; the word jaw used in the singular typically refers to the lower jaw.
The upper jaw or maxilla is more or less fixed with the skull and is composed of two bones, the maxillae, fused intimately at the median line by a suture; incomplete closure of this suture and surrounding structures may be involved in the malformation known as cleft palate.
The maxillary bones form parts of the roof of the mouth, the floor and sides of the nasal cavity, and the floor of the orbit or eye socket.
The jaws typically accommodate the teeth or form the bases for the attachment of a beak.

The jaw in fish and amphibians

The vertebrate jaw probably originally evolved in the Silurian period and appeared in the Placoderm fish which further diversified in the Devonian. Jaws are thought to derive from the pharyngeal arches that support the gills in fish. The two most anterior of these arches are thought to have become the jaw itself and the hyoid arch, which braces the jaw against the braincase and increases mechanical efficiency. While there is no fossil evidence directly to support this theory, it makes sense in light of the numbers of pharyngeal arches that are visible in extant jawed (the Gnathostomes), which have seven arches, and primitive jawless vertebrates (the Agnatha), which have nine.
It is thought that the original selective advantage garnered by the jaw was not related to feeding, but to increased respiration efficiency. The jaws were used in the buccal pump (observable in modern fish and amphibians) that pumps water across the gills of fish or air into the lungs in the case of amphibians. Over evolutionary time the more familiar use of jaws (to humans), in feeding, was selected for and became a very important function in vertebrates.

The jaw in reptiles

In reptiles, the mandible is made up of five bones. In the evolution of mammals, four of these bones were reduced in size and incorporated into the ear. In their reduced form, they are known as the malleus and incus; along with the more ancient stapes, they are the ossicles. This adaptation is advantageous, not only because a one-bone jaw is stronger, but also because the malleus and incus improve hearing. (However, reptiles tend to swallow prey whole because their pace of digestion is different than mammals, so multiple jaw bones may allow flexibility to expand the jaws around prey.)

See also

jaw in Arabic: فك
jaw in Czech: Čelist
jaw in German: Kiefer (Anatomie)
jaw in Esperanto: Makzelo
jaw in Spanish: Maxilar
jaw in French: Mâchoire
jaw in Indonesian: Rahang
jaw in Hebrew: לסת
jaw in Hungarian: Állcsont
jaw in Dutch: Kaak
jaw in Narom: Mâchouaile
jaw in Japanese: 顎
jaw in Polish: Żuchwa
jaw in Portuguese: Mandíbula
jaw in Swedish: Käke
jaw in Ukrainian: Щелепи
jaw in Tagalog: Panga

Synonyms, Antonyms and Related Words

abuse, babble, bark at, baste, bat the breeze, bazoo, beat the gums, berate, betongue, blab, blabber, blacken, blather, blether, carpet, chaps, chat, chatter, chin, chops, clack, clatter, dither, embouchure, execrate, fulminate against, gab, gabble, gas, gibber, gibble-gabble, go on, gob, gossip, gush, haver, jabber, jaws, jowls, kisser, lip, lips, load with reproaches, mandibles, maw, maxilla, mouth, mug, mush, muzzle, natter, oral cavity, palaver, patter, pour forth, prate, prattle, premaxilla, rag, rail, rail at, ramble on, rate, rattle, rattle on, rave against, reel off, revile, run on, sass, sauce, shoot the breeze, spiel, spout, spout off, talk away, talk nonsense, talk on, thunder against, tittle-tattle, tongue-lash, trap, twaddle, twattle, upbraid, vilify, vituperate, waffle, wig, yak, yakkety-yak, yap, yell at, yelp at
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