The Collaborative International Dictionary of English v.0.48:

Bend \Bend\, n. [AS. bend. See Band, and cf. the preceding
   noun.]
   1. A band. [Obs.] --Spenser.
      [1913 Webster]

   2. [OF. bende, bande, F. bande. See Band.] (Her.) One of
      the honorable ordinaries, containing a third or a fifth
      part of the field. It crosses the field diagonally from
      the dexter chief to the sinister base.
      [1913 Webster]

   Bend sinister (Her.), an honorable ordinary drawn from the
      sinister chief to the dexter base.
      [1913 Webster]

WordNet (r) 3.0 (2006):

bend sinister
    n 1: a mark of bastardy; lines from top right to bottom left
         [syn: bar sinister, bend sinister]