countermine

Plural: countermines

Noun

• (military) a tunnel dug to defeat similar activities by the enemy
• A mine used by defenders to intercept an enemy mine or tunnel.
• An underground gallery excavated to intercept and destroy the mining of an enemy.
• A stratagem or plot by which another stratagem or project is defeated.

Verb

• destroy property or hinder normal operations
• destroy enemy mines with one's own mines
  • "We countermined the banks of the river"
• To plot opposition; to frustrate the initiatives of another.
• to sap hostile mining.

Synonyms

counteract, sabotage, subvert, undermine, weaken, counterplot