The Collaborative International Dictionary of English v.0.48:

Corbel \Cor"bel\ (k[^o]r"b[e^]l), n. [F. corbeau, for older
   corbel, dim. of L. corbis basket. (Corbels were often in the
   form of a basket.) See Corbeil.] (Arch.)
   A bracket supporting a superincumbent object, or receiving
   the spring of an arch. Corbels were employed largely in
   Gothic architecture.
   [1913 Webster]

   Note: A common form of corbel consists of courses of stones
         or bricks, each projecting slightly beyond the next
         below it.
         [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Corbel \Cor"bel\, v. t.
   To furnish with a corbel or corbels; to support by a corbel;
   to make in the form of a corbel.
   [1913 Webster]

   To corbel out, to furnish with a corbel of courses, each
      projecting beyond the one next below it.
      [1913 Webster]

WordNet (r) 3.0 (2006):

corbel
    n 1: (architecture) a triangular bracket of brick or stone
         (usually of slight extent) [syn: corbel, truss]
    v 1: furnish with a corbel