1. Pharmacology. a chemical substance used in the treatment, cure, prevention, or diagnosis of disease or used to otherwise enhance physical or mental well-being.
2. a. any substance recognized in the official pharmacopoeia or formulary of the nation.
b. any substance intended for use in the diagnosis, cure, mitigation, treatment, or prevention of disease in humans or other animals.
c. any article, other than food, intended to affect the structure or any function of the body of humans or other animals.
d. any substance intended for use as a component of such a drug, but not a device or a part of a device.
3. a habit-forming medicinal or illicit substance, especially a narcotic.
1. any substance or substances used in treating disease or illness; medicament; remedy.
2. the art or science of restoring or preserving health or due physical condition, as by means of drugs, surgical operations or appliances, or manipulations: often divided into medicine proper, surgery, and obstetrics.
3. the art or science of treating disease with drugs or curative substances, as distinguished from surgery and obstetrics.