Source : Webster's Revised Unabridged Dictionary (1913)

Tenon \Ten"on\, v. t.
   To cut or fit for insertion into a mortise, as the end of a
   piece of timber.

Tenon \Ten"on\, n. [F., fr. tenir to hold. See {Tenable}.]
   (Carp. & Join.)
   A projecting member left by cutting away the wood around it,
   and made to insert into a mortise, and in this way secure
   together the parts of a frame; especially, such a member when
   it passes entirely through the thickness of the piece in
   which the mortise is cut, and shows on the other side. Cf.
   {Tooth}, {Tusk}.

   {Tenon saw}, a saw with a thin blade, usually stiffened by a
      brass or steel back, for cutting tenons. [Corruptly
      written {tenant saw}.] --Gwilt.

Source : WordNet®

tenon
     n : a projection at the end of a piece of wood that is shaped to
         fit into a mortise and form a mortise joint