noun pl. placebos -·bos or placeboes -·boes

1. R.C.Ch. the first antiphon of the vespers for the dead, beginning with the word placebo
2. a harmless, unmedicated preparation given as a medicine merely to humor a patient, or used as a control in testing the efficacy of another, medicated substance
3. something said or done to win the favor of another

Etymology: ME < L, I shall please