The Collaborative International Dictionary of English v.0.48:

Miter \Mi"ter\, Mitre \Mi"tre\, v. t. [imp. & p. p. Miteredor
   Mitred; p. pr. & vb. n. Miteringor Mitring.]
   1. To place a miter upon; to adorn with a miter. [WordNet
      sense 2] "Mitered locks." --Milton.
      [1913 Webster]

   2. To match together, as two pieces of molding or brass rule
      on a line bisecting the angle of junction; to fit together
      in a miter joint. [WordNet sense 3]
      [1913 Webster]

   3. To bevel the ends or edges of, for the purpose of matching
      together at an angle. [WordNet sense 1]
      [1913 Webster] Miter