The Collaborative International Dictionary of English v.0.48:

Ligation \Li*ga"tion\ (l[-i]*g[=a]"sh[u^]n), n. [L. ligatio, fr.
   ligare to bind. Cf. Liaison.]
   1. The act of binding, or the state of being bound.
      [1913 Webster]

   2. That which binds; bond; connection.
      [1913 Webster]

            Tied with tape, and sealed at each fold and
            ligation.                             --Sir W.
                                                  Scott.
      [1913 Webster]

WordNet (r) 3.0 (2006):

ligation
    n 1: (surgery) tying a duct or blood vessel with a ligature (as
         to prevent bleeding during surgery)