countermine

Short definition from Wiktionary

Noun

1. 1
   A mine used by defenders to intercept an enemy mine or tunnel.
2. 2
   An underground gallery excavated to intercept and destroy the mining of an enemy.
3. 3
   A stratagem or plot by which another stratagem or project is defeated.

Verb

1. 1
   To plot opposition; to frustrate the initiatives of another.
2. 2
   to sap hostile mining.