intoxicant

1. General: Substance which when taken into a body by one mean or another produces a condition of diminished mental and physical ability, hyperexcitability, or stupefaction. Commonly, a beverage is classified as an intoxicating when its alcoholic content is 0.5 percent or more.

2. Medicine: Substance that poisons or produces symptoms of poisoning in a body. From Greek 'toxicon,' poison.