pla ‧ ce ‧ bo /pləˈsiːbəʊ $ -boʊ/ BrE AmE noun ( plural placebos ) [countable]
[ Date: 1700-1800 ; Language: Latin ; Origin: 'I shall please' , from placere ; ⇨ ↑ please 2 ]
1 . a harmless substance given to a sick person instead of medicine, without telling them it is not real. Placebos are often used in tests in which some people take real medicine and others take a placebo, so that doctors can compare the results to see if the real medicine works properly.
2 . placebo effect when someone feels better after taking a placebo, even though it has not had any effect on their body