ataractic n a drug used to reduce stress or tension without reducing mental clarity s tending to soothe or tranquilize Usage(s) Trade-named Librium by New Jersey's Roche Laboratories, it is technically methamino-diazepoxide, a synthetic chemical unrelated to previous ataractic drugs. Others cannot tolerate it if they have taken antihistamine or ataractic drugs. Synonym(s) tranquilizer tranquillizer tranquilliser antianxiety agent ataractic drug ataractic agent ataraxic sedative tranquilizing tranquillizing tranquilising tranquillising