countermine

From counter- +‎ mine.

countermine (plural countermines)

1. A mine used by defenders to intercept an enemy mine or tunnel.
   • 1990, Peter Hopkirk, The Great Game, Folio Society 2010, p. 436:

     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.
   • Sir Philip Sidney

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

countermine (third-person singular simple present countermines, present participle countermining, simple past and past participle countermined)

1. To plot opposition; to frustrate the initiatives of another.
   • 1749, Henry Fielding, chapter III, in The History of Tom Jones, a Foundling. In Six Volumes, volume (please specify |volume=I to VI), London: Printed by A[ndrew] Millar, […], OCLC 928184292, book VI:

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

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

• (to plot opposition): counterplot