drug (drŭg)

1. A substance used in the diagnosis, treatment, or prevention of a disease or as a component of a medication.
2. Such a substance as recognized or defined by the US Food and Drug Administration.
3. A chemical substance, such as a narcotic or hallucinogen, that affects the central nervous system, causing changes in behavior and often addiction.

1. To administer a drug, especially in an overly large quantity, to an individual.
2. To stupefy or dull with or as if with a drug; to narcotize.