The Collaborative International Dictionary of English v.0.48:

Joint \Joint\ (joint), n. [F. joint, fr. joindre, p. p. joint.
   See Join.]
   [1913 Webster]
   1. The place or part where two things or parts are joined or
      united; the union of two or more smooth or even surfaces
      admitting of a close-fitting or junction; junction; as, a
      joint between two pieces of timber; a joint in a pipe.
      [1913 Webster]

   2. A joining of two things or parts so as to admit of motion;
      an articulation, whether movable or not; a hinge; as, the
      knee joint; a node or joint of a stem; a ball and socket
      joint. See Articulation.
      [1913 Webster]

            A scaly gauntlet now, with joints of steel,
            Must glove this hand.                 --Shak.
      [1913 Webster]

            To tear thee joint by joint.          --Milton.
      [1913 Webster]

   3. The part or space included between two joints, knots,
      nodes, or articulations; as, a joint of cane or of a grass
      stem; a joint of the leg.
      [1913 Webster]

   4. Any one of the large pieces of meat, as cut into portions
      by the butcher for roasting.
      [1913 Webster]

   5. (Geol.) A plane of fracture, or divisional plane, of a
      rock transverse to the stratification.
      [1913 Webster]

   6. (Arch.) The space between the adjacent surfaces of two
      bodies joined and held together, as by means of cement,
      mortar, etc.; as, a thin joint.
      [1913 Webster]

   7. The means whereby the meeting surfaces of pieces in a
      structure are secured together.
      [1913 Webster]

   8. [Jag a notch.] A projecting or retreating part in
      something; any irregularity of line or surface, as in a
      wall. [Now Chiefly U. S.]
      [Webster 1913 Suppl.]

   9. (Theaters) A narrow piece of scenery used to join together
      two flats or wings of an interior setting.
      [Webster 1913 Suppl.]

   10. a disreputable establishment, or a place of low resort,
       as for smoking opium; -- also used for a commercial
       establishment, implying a less than impeccable
       reputation, but often in jest; as, talking about a
       high-class joint is an oxymoron. [Slang]
       [Webster 1913 Suppl. +PJC]

   11. a marijuana cigarette. [Slang]
       [PJC]

   12. prison; -- used with "the". [Slang] " he spent five years
       in the joint."
       [PJC]

   Coursing joint (Masonry), the mortar joint between two
      courses of bricks or stones.

   Fish joint, Miter joint, Universal joint, etc. See
      under Fish, Miter, etc.

   Joint bolt, a bolt for fastening two pieces, as of wood,
      one endwise to the other, having a nut embedded in one of
      the pieces.

   Joint chair (Railroad), the chair that supports the ends of
      abutting rails.

   Joint coupling, a universal joint for coupling shafting.
      See under Universal.

   Joint hinge, a hinge having long leaves; a strap hinge.

   Joint splice, a re["e]nforce at a joint, to sustain the
      parts in their true relation.

   Joint stool.
       (a) A stool consisting of jointed parts; a folding stool.
           --Shak.
       (b) A block for supporting the end of a piece at a joint;
           a joint chair.

   Out of joint, out of place; dislocated, as when the head of
      a bone slips from its socket; hence, not working well
      together; disordered. "The time is out of joint." --Shak.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Miter \Mi"ter\, Mitre \Mi"tre\, n. [F. mitre, fr. L. mitra
   headband, turban, Gr. ?.]
   1. A covering for the head, worn on solemn occasions by
      bishops and other church dignitaries. It has been made in
      many forms, the present form being a lofty cap with two
      points or peaks. --Fairholt.
      [1913 Webster]

   2. The surface forming the beveled end or edge of a piece
      where a miter joint is made; also, a joint formed or a
      junction effected by two beveled ends or edges; a miter
      joint.
      [1913 Webster]

   3. (Numis.) A sort of base money or coin.
      [1913 Webster]

   Miter box (Carp. & Print.), an apparatus for guiding a
      handsaw at the proper angle in making a miter joint; esp.,
      a wooden or metal trough with vertical kerfs in its
      upright sides, for guides.

   Miter dovetail (Carp.), a kind of dovetail for a miter
      joint in which there is only one joint line visible, and
      that at the angle.

   Miter gauge (Carp.), a gauge for determining the angle of a
      miter.

   Miter joint, a joint formed by pieces matched and united
      upon a line bisecting the angle of junction, as by the
      beveled ends of two pieces of molding or brass rule, etc.
      The term is used especially when the pieces form a right
      angle, such as the edges of a window frame, and the edge
      of each piece at the point of junction is cut at a 45[deg]
      angle to its long direction. See Miter, 2.

   Miter shell (Zool.), any one of numerous species of marine
      univalve shells of the genus Mitra.

   Miter square (Carp.), a bevel with an immovable arm at an
      angle of 45[deg], for striking lines on stuff to be
      mitered; also, a square with an arm adjustable to any
      angle.

   Miter wheels, a pair of bevel gears, of equal diameter,
      adapted for working together, usually with their axes at
      right angles.
      [1913 Webster] Miter

WordNet (r) 3.0 (2006):

miter joint
    n 1: joint that forms a corner; usually both sides are bevelled
         at a 45-degree angle to form a 90-degree corner [syn:
         miter joint, mitre joint, miter, mitre]