Definition of placebo noun from the Oxford Advanced Learner's Dictionary

 

placebo

 noun
noun
BrE BrE//pləˈsiːbəʊ//
 
; NAmE NAmE//pləˈsiːboʊ//
 
(pl. placebos) Medication
 
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a substance that has no physical effects, given to patients who do not need medicine but think that they do, or used when testing new drugs the placebo effect (= the effect of taking a placebo and feeling better) Half of the people taking part in the experiment were given a placebo. The placebo effect means that any treatment will improve patients merely because they want to recover. Wordfinderadminister, capsule, dispense, dose, ill, inhaler, medicine, medication, pharmacy, placebo See related entries: Medication Word Origin late 18th cent.: from Latin, literally ‘I shall be acceptable or pleasing’, from placere ‘to please’.
See the Oxford Advanced American Dictionary entry: placebo