countermine

noun

1. A mine used by defenders to intercept an enemy mine or tunnel.

   “Normally the threat would have been dealt with by means of a counter-mine, but the tunnel was now far too close for that.”

2. An underground gallery excavated to intercept and destroy the mining of an enemy.
3. A stratagem or plot by which another stratagem or project is defeated.

   “Thinking himself contemned, knowing no countermine against contempt but terror.”

verb

1. To plot opposition; to frustrate the initiatives of another.

   “[…] every gamester will agree how necessary it is to know exactly the play of another, in order to countermine him.”

2. (intransitive, transitive)to sap hostile mining.

   “[…]so Fritz could sleep easily in his trench, so far as mines were concerned; and Fritz, confident in his Herr Professors, altogether neglected any attempt to counter-mine.”