erad·i·cant I. \-kənt\adjective Etymology:eradicate + -ant : acting or tending to act as a pesticidal eradicant < an eradicant spray > II. noun (-s) : an agent of eradication; especially: a pesticidal spray used to destroy a parasitic organism at its source before it reaches the suscept < an eradicant applied to scab-infested apple leaves on the ground > — compare protectant