The Collaborative International Dictionary of English v.0.48:

Obtund \Ob*tund"\, v. t. [imp. & p. p. Obtunded; p. pr. & vb.
   n. Obtunding.] [L. obtundere, obtusum; ob (see Ob-) +
   tundere to strike or beat. See Stutter.]
   To reduce the edge, pungency, or violent action of; to dull;
   to blunt; to deaden; to quell; as, to obtund the acrimony of
   the gall. [Archaic] --Harvey.
   [1913 Webster]

         They . . . have filled all our law books with the
         obtunding story of their suits and trials. --Milton.
   [1913 Webster]

WordNet (r) 3.0 (2006):

obtund
    v 1: reduce the edge or violence of; "obtunded reflexes"