jaw breaker

Jaw \Jaw\ (j[add]), n. [A modification of chaw, formed under the
   influence of F. joue the cheek. See {Chaw}, {Chew}.]
   [1913 Webster]
   1. (Anat.)
      (a) One of the bones, usually bearing teeth, which form
          the framework of the mouth.
      (b) Hence, also, the bone itself with the teeth and
          covering.
      (c) In the plural, the mouth.
          [1913 Webster]

   2. Fig.: Anything resembling the jaw of an animal in form or
      action; esp., pl., the mouth or way of entrance; as, the
      jaws of a pass; the jaws of darkness; the jaws of death.
      --Shak.
      [1913 Webster]

   3. (Mach.)
      (a) A notch or opening.
      (b) A notched or forked part, adapted for holding an
          object in place; as, the jaw of a railway-car
          pedestal. See {Axle guard}.
      (b) 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.
          [1913 Webster]

   4. (Naut.) The inner end of a boom or gaff, hollowed in a
      half circle so as to move freely on a mast.
      [1913 Webster]

   5. Impudent or abusive talk. [Slang] --H. Kingsley.

   Syn: lip.
        [1913 Webster]

   {Jaw bit} (Railroad), a bar across the jaws of a pedestal
      underneath an axle box.

   {Jaw breaker}, a word difficult to pronounce. [Obs.]

   {Jaw rope} (Naut.), a rope which holds the jaws of a gaff to
      the mast.

   {Jaw tooth}, a molar or grinder; a back tooth.
      [1913 Webster]