Source : Webster's Revised Unabridged Dictionary (1913)

Hinge \Hinge\, n. [OE. henge, heeng; akin to D. heng, LG. henge,
   Prov. E. hingle a small hinge; connected with hang, v., and
   Icel. hengja to hang. See {Hang}.]
   1. The hook with its eye, or the joint, on which a door,
      gate, lid, etc., turns or swings; a flexible piece, as a
      strip of leather, which serves as a joint to turn on.

            The gate self-opened wide, On golden hinges turning.
                                                  --Milton.

   2. That on which anything turns or depends; a governing
      principle; a cardinal point or rule; as, this argument was
      the hinge on which the question turned.

   3. One of the four cardinal points, east, west, north, or
      south. [R.]

            When the moon is in the hinge at East. --Creech.

            Nor slept the winds . . . but rushed abroad.
                                                  --Milton.

   {Hinge joint}.
      (a) (Anat.) See {Ginglymus}.
      (b) (Mech.) Any joint resembling a hinge, by which two
          pieces are connected so as to permit relative turning
          in one plane.

   {To be off the hinges}, to be in a state of disorder or
      irregularity; to have lost proper adjustment. --Tillotson.

Source : WordNet®

hinge joint
     n 1: a freely moving joint in which the bones are so articulated
          as to allow extensive movement in one plane [syn: {ginglymus},
           {ginglymoid joint}]
     2: a joint allowing movement in one plane only [syn: {knuckle
        joint}]