Source : Webster's Revised Unabridged Dictionary (1913)

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.

   2. To frustrate or counteract by secret measures.