Source : Webster's Revised Unabridged Dictionary (1913)

Mortise \Mor"tise\, n. [F. mortaise; cf. Sp. mortaja, Ar.
   murtazz fixed, or W. mortais, Ir. mortis, moirtis, Gael.
   moirteis.]
   A cavity cut into a piece of timber, or other material, to
   receive something (as the end of another piece) made to fit
   it, and called a tenon.

   {Mortise and tenon} (Carp.), made with a mortise and tenon;
      joined or united by means of a mortise and tenon; -- used
      adjectively.

   {Mortise joint}, a joint made by a mortise and tenon.

   {Mortise lock}. See under {Lock}.

   {Mortise wheel}, a cast-iron wheel, with wooden clogs
      inserted in mortises on its face or edge; -- also called
      {mortise gear}, and {core gear}.

Source : WordNet®

mortise joint
     n 1: a gliding joint between the distal ends of the tibia and
          fibula and the proximal end of the talus [syn: {ankle},
          {ankle joint}, {articulatio talocruralis}]
     2: a joint made by inserting tenon on one piece into mortise
        holes in the other [syn: {mortise-and-tenon joint}]