drug (dr?g)n.1. a. A substance used in the diagnosis, treatment, or prevention of a disease or as a component of a medication.b. Such a substance as recognized or defined by the US Food, Drug, and Cosmetic Act.2. A chemical substance, such as a narcotic or hallucinogen, that affects the central nervous system, causing changes in behavior and often addiction.3. Obsolete A chemical or dye.tr.v. drugged, drug·ging, drugs 1. a. To administer a drug to, especially to treat pain or induce anesthesia.b. To give a drug to, especially surreptitiously, in order to induce stupor. 2. To poison or mix (food or drink) with a drug.[Middle English drogge, from Old French drogue, drug, perhaps from Middle Dutch droge (vate), dry (cases), pl. of drog, dry.]American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.drug (dr??) n1. (Pharmacology) any synthetic, semisynthetic, or natural chemical substance used in the treatment, prevention, or diagnosis of disease, or for other medical reasons. 2. (Recreational Drugs) a chemical substance, esp a narcotic, taken for the pleasant effects it produces3. (Commerce) drug on the market a commodity available in excess of the demands of the marketvb (tr) , drugs, drugging or drugged4. (Cookery) to mix a drug with (food, drink, etc)5. (Pharmacology) to administer a drug to6. (Pharmacology) to stupefy or poison with or as if with a drug[C14: from Old French drogue, probably of Germanic origin] ?druggy adjCollins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014drug1 (dr?g) n., v. drugged, drug?ging. n. 1. a chemical substance used in the treatment, cure, prevention, or diagnosis of disease or to otherwise enhance physical or mental well-being. 2. (in federal law) a. any substance listed in any of the recognized pharmacopoeias. b. any substance intended for use in the treatment or prevention of disease. c. any nonfood substance intended to affect any function of the body. d. any component of such a drug. 3. a habit-forming medicinal or illicit substance, esp. a narcotic. 4. drugs, chemical substances prepared and sold as pharmaceutical items either by prescription or over the counter. 5. Obs. any ingredient used in chemistry, pharmacy, dyeing, or the like. v.t. 6. to administer a medicinal drug to. 7. to stupefy or poison with a drug. 8. to mix (food or drink) with a drug, esp. a stupefying, narcotic or poisonous drug. Idioms: drug on the market, a commodity that is overabundant or not in demand in the market. [1300?50; Middle English drogges (pl.)