n. Milit., a mine driven from defense-works by the besieged, counter to a mine driven toward the defense-works by besiegers, the object being to meet and destroy the works of the latter party.n. Hence A secret plan designed to frustrate the plans of an opponent; any antagonistic action or plan.To mine counter or in opposition to; resist by means of a countermine, as a besieging enemy or his works.To counterwork; frustrate by secret and opposite measures.To make a countermine; counterplot; work against one secretly.n. A mine or torpedo placed and exploded in a harbor entrance by an attacking navy to destroy the mines or torpedoes which guard the entrance.