nausea: the state that precedes vomiting
symptom: (medicine) any sensation or change in bodily function that is experienced by a patient and is associated with a particular disease
organophosphate nerve agent: any of a series of nerve agents containing organophosphate compounds first synthesized by German chemists in 1936; in World War II the Germans tested them in concentration camps but not on the battlefield; Iraq is alleged to have used them against Iran and against the Kurds