counter-ˈagent [counter- 2.] A counteracting agent or force; a counteractant. 1826–56De Quincey Confess. (1862) p. viii, The properties, counter-agents, etc., of this drug.1868Gladstone Juv. Mundi xi. (1870) 449 Reverence..the counter-agent to all meanness and selfishness.