The Collaborative International Dictionary of English v.0.48:

Drug \Drug\ (dr[u^]g), v. i. [See 1st Drudge.]
   To drudge; to toil laboriously. [Obs.] "To drugge and draw."
   --Chaucer.
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The Collaborative International Dictionary of English v.0.48:

Drug \Drug\, n.
   A drudge (?). --Shak. (Timon iv. 3, 253).
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The Collaborative International Dictionary of English v.0.48:

Drug \Drug\, n. [F. drogue, prob. fr. D. droog; akin to E. dry;
   thus orig., dry substance, hers, plants, or wares. See
   Dry.]
   1. Any animal, vegetable, or mineral substance used in the
      composition of medicines.
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            Whence merchants bring
            Their spicy drugs. --Milton.
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   2. Any commodity that lies on hand, or is not salable; an
      article of slow sale, or in no demand; -- used often in
      the phrase "a drug on the market". "But sermons are mere
      drugs." --Fielding.
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            And virtue shall a drug become.       --Dryden.
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   3. any stuff used in dyeing or in chemical operations.
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   4. any substance intended for use in the treatment,
      prevention, diagnosis, or cure of disease, especially one
      listed in the official pharmacopoeia published by a
      national authority.
      [PJC]

   5. any substance having psychological effects, such as a
      narcotic, stimulant, or hallucinogenic agent, especially
      habit-forming and addictive substances, sold or used
      illegally; as, a drug habit; a drug treatment program; a
      teenager into drugs; a drug bust; addicted to drugs; high
      on drugs.

   Syn: illegal drug. [PJC]

              They [smaller and poorer nations] have lined up to
              recount how drug trafficking and consumption have
              corrupted their struggling economies and societies
              and why they are hard pressed to stop it. --
                                                  Christopher S.
                                                  Wren (N Y.
                                                  Times, June
                                                  10, 1998, p.
                                                  A5)
        [PJC]

The Collaborative International Dictionary of English v.0.48:

Drug \Drug\, v. i. [imp. & p. p. Drugged; p. pr. & vb. n.
   Drugging.] [Cf. F. droguer.]
   To prescribe or administer drugs or medicines. --B. Jonson.
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The Collaborative International Dictionary of English v.0.48:

Drug \Drug\, v. t.
   1. To affect or season with drugs or ingredients; esp., to
      stupefy by a narcotic drug. Also Fig.
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            The laboring masses . . . [were] drugged into
            brutish good humor by a vast system of public
            spectacles.                           --C. Kingsley.
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            Drug thy memories, lest thou learn it. --Tennyson.
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   2. To tincture with something offensive or injurious.
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            Drugged as oft,
            With hatefullest disrelish writhed their jaws.
                                                  --Milton.
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   3. To dose to excess with, or as with, drugs.
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            With pleasure drugged, he almost longed for woe.
                                                  --Byron.
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WordNet (r) 3.0 (2006):

drug
    n 1: a substance that is used as a medicine or narcotic
    v 1: administer a drug to; "They drugged the kidnapped tourist"
         [syn: drug, dose]
    2: use recreational drugs [syn: drug, do drugs]

Moby Thesaurus II by Grady Ward, 1.0:

152 Moby Thesaurus words for "drug":
   Adrenalin, Benzedrine, Dexamyl, Dexedrine, KO, Methedrine,
   Mickey Finn, aloes, ammonium carbonate, amphetamine,
   amphetamine sulphate, analgesic, anesthetic, anesthetize, anoint,
   antidepressant, article, article of commerce,
   article of merchandise, balm, balsam, bedaze, belladonna, benumb,
   benzoin, besot, bismuth, blunt, caffeine, chloroform, chocolate,
   cocaine, cocoa, coffee, coldcock, colocynth, commodity, cure,
   cure-all, deaden, desensitize, desoxyephedrine,
   dextroamphetamine sulfate, dope, dose, downer, drops, dull,
   electuary, elixir, embrocate, entrance, ergot, etherize,
   ethical drug, feature, freeze, generic name, hallucinogenic, herbs,
   hop, hypnotic, hypnotize, inhalant, item, kayo, knock out,
   knock senseless, knock stiff, knock unconscious, knockout drop,
   kola, kola nut, lay out, lead item, leader, lincture, linctus,
   loss leader, lull to sleep, magnetize, materia medica, medicament,
   medicate, medication, medicinal, medicinal herbs, medicine,
   mesmerize, methamphetamine hydrochloride, mixture, narcotic,
   narcotize, nonprescription drug, numb, obtund, officinal, oil,
   opiate, pain-killer, palsy, panacea, paralyze, patent medicine,
   pharmaceutical, pharmacon, physic, poison, powder, preparation,
   prescription drug, product, proprietary, proprietary medicine,
   proprietary name, psychedelic, put to sleep, put under, quinine,
   remedy, rock to sleep, sal ammoniac, salve, sassafras, seconds,
   sedate, sedative, simple, simples, sleeping pill, soporific,
   special, specific, standard article, staple, staple item,
   stimulant, strychnine, stun, stupefy, syrup, tea, theraputant,
   tisane, trance, tranquilizer, treat, treatment, upper,
   vegetable remedies, vendible, ware