The Collaborative International Dictionary of English v.0.48:

Countermine \Coun`ter*mine"\ (koun`t[~e]r*m[imac]n"), v. t. [Cf.
   F. contreminer.] [imp. & p. p. Countermined; p. pr. & vb.
   n. Countermining.]
   1. (Mil.) To oppose by means of a countermine; to intercept
      with a countermine.
      [1913 Webster]

   2. To frustrate or counteract by secret measures.
      [1913 Webster]