The Collaborative International Dictionary of English v.0.48:

Mortise \Mor"tise\, v. t. [imp. & p. p. Mortised; p. pr. & vb.
   n. Mortising.]
   1. To cut or make a mortise in.
      [1913 Webster]

   2. To join or fasten by a tenon and mortise; as, to mortise a
      beam into a post, or a joist into a girder.
      [1913 Webster]