drug  
 noun [ C ] uk/drʌɡ/ us/drʌɡ/
  (MEDICINE)      
 B2 药,药物,药品
any natural or artificially made chemical that is used as a medicine
  anti-cancer/fertility/pain-killing drugs 抗癌/治疗不育症/止疼药 
 a prescription drug 处方药 
 drug therapy 药物治疗 
 He takes several drugs for his condition. 为了治病他要吃好几种药。 
 - More examples
 - The new drug could be an important step in the fight against cancer.
 - There are doubts about the effectiveness of the new drug in treating the disease.
 - For patients who do not respond to drug treatment, surgery is a possible option.
 - The doctors gave him more powerful drugs in the vain hope that he might recover.
 - I can give you stronger pain-killing drugs if these aren't strong enough.
 
  (ILLEGAL SUBSTANCE)         
B2 毒品;兴奋剂
any natural or artificially made chemical that is taken for pleasure, to improve someone's performance of an activity, or because a person cannot stop using it
  illegal drugs 毒品 
 a drug addict 吸毒成瘾者 
 drug addiction/abuse 毒瘾/滥用毒品 
 She began to suspect that her son was on/taking/doing drugs. 她开始怀疑儿子在吸毒。 
 She was suspected of being a drug dealer. 她被怀疑是毒品贩子。 
 His son died of a drug overdose. 他的儿子因吸毒过量而死亡。 
  成瘾之事
any activity that you cannot stop doing
  Work is a drug for him. 他是个工作狂。 
 - More examples
 - The government are to step up their attempt to wage war on drugs.
 - "I'm arresting you on suspicion of illegally possessing drugs, " said the police officer.
 - The athlete was given a stiff punishment for using drugs.
 - Police found a small quantity of drugs in his possession.
 - Desperate measures are needed to deal with the growing drug problem.
 
drug       
verb [ T ] uk/drʌɡ/ us/drʌɡ/ -gg-
 用药麻醉,对…施用麻醉剂
to give a person or animal a chemical that causes him, her, or it to lose feeling or become unconscious
  The killer confessed that he often drugged his victims before he killed them. 那名杀手供认在杀人之前他通常对受害者使用麻醉剂。 
 She was heavily drugged to ease the pain. 给她打了大量的麻醉剂来缓解疼痛。 
UK informal We visited her in hospital but she was drugged to the eyeballs (= had been given a lot of drugs) and I don't think she even knew we were there. 我们去医院看她时她已经打了大量的麻药,我想她都不知道我们去看过她。