The Collaborative International Dictionary of English v.0.48:

Rabbet \Rab"bet\ (r[a^]b"b[e^]t), v. t. [imp. & p. p.
   Rabbeted; p. pr. & vb. n. Rabbeting.] [F. raboter to
   plane, plane down,rabot a plane; pref. re- re- + OF. abouter,
   aboter. See Abut, and cf. Rebut.]
   1. To cut a rabbet in; to furnish with a rabbet.
      [1913 Webster]

   2. To unite the edges of, as boards, etc., in a rabbet joint.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Rabbet \Rab"bet\, n. [See Rabbet, v., and cf. Rebate, n.]
   [1913 Webster]
   1. (Carp.) A longitudinal channel, groove, or recess cut out
      of the edge or face of any body; especially, one intended
      to receive another member, so as to break or cover the
      joint, or more easily to hold the members in place; thus,
      the groove cut for a panel, for a pane of glass, or for a
      door, is a rabbet, or rebate.
      [1913 Webster]

   2. Same as Rabbet joint, below.
      [1913 Webster]

   Rabbet joint (Carp.), a joint formed by fitting together
      rabbeted boards or timbers; -- called also rabbet.

   Rabbet plane, a joiner's plane for cutting a rabbet.
      --Moxon.
      [1913 Webster]

WordNet (r) 3.0 (2006):

rabbet
    n 1: a rectangular groove made to hold two pieces together [syn:
         rabbet, rebate]
    v 1: join with a rabbet joint
    2: cut a rectangular groove into