placebo definition | Dictionary.com

pla⋅ce⋅bo

[pluh-see-boh for 1; plah-chey-boh for 2]

–noun, plural -bos, -boes.

Medicine/Medical, Pharmacology.

a.	a substance having no pharmacological effect but given merely to satisfy a patient who supposes it to be a medicine.

b.	a substance having no pharmacological effect but administered as a control in testing experimentally or clinically the efficacy of a biologically active preparation.

2.	Roman Catholic Church. the vespers of the office for the dead: so called from the initial word of the first antiphon, taken from Psalm 114:9 of the Vulgate.

Origin:
1175–1225 for def. 2; 1775–85 for def. 1; ME < L placēbō I shall be pleasing, acceptable

Dictionary.com Unabridged (v 1.1)
Based on the Random House Unabridged Dictionary, © Random House, Inc. 2006.
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American Heritage Dictionary - Cite This Source - Share This

pla·ce·bo (plə-sē'bō) Pronunciation Key
n. pl. pla·ce·bos or pla·ce·boes

1. A substance containing no medication and prescribed or given to reinforce a patient's expectation to get well.
2. An inactive substance or preparation used as a control in an experiment or test to determine the effectiveness of a medicinal drug.
Something of no intrinsic remedial value that is used to appease or reassure another.
(plä-chā'bō) Roman Catholic Church The service or office of vespers for the dead.

[Middle English, from Late Latin placēbō, I shall please (the first word of the first antiphon of the service), first person sing. future tense of Latin placēre, to please; see plāk-¹ in Indo-European roots.]

The American Heritage® Dictionary of the English Language, Fourth Edition
Copyright © 2006 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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Online Etymology Dictionary - Cite This Source - Share This
placebo

c.1225, name given to the rite of Vespers of the Office of the Dead, so called from the opening of the first antiphon, "I will please the Lord in the land of the living" (Psalm cxiv:9), from L. placebo "I shall please," future indic. of placere "to please" (see please). Medical sense is first recorded 1785, "a medicine given more to please than to benefit the patient."

Online Etymology Dictionary, © 2001 Douglas Harper
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WordNet - Cite This Source - Share This

placebo
noun
1.	an innocuous or inert medication; given as a pacifier or to the control group in experiments on the efficacy of a drug
2.	(Roman Catholic Church) vespers of the office for the dead

WordNet® 3.0, © 2006 by Princeton University.
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The American Heritage Science Dictionary - Cite This Source - Share This

placebo (plə-sē'bō) Pronunciation Key

A substance containing no medication and prescribed to reinforce a patient's expectation of getting well or used as a control in a clinical research trial to determine the effectiveness of a potential new drug.

The American Heritage® Science Dictionary
Copyright © 2002 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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American Heritage New Dictionary of Cultural Literacy, Third Edition - Cite This Source - Share This
placebo [(pluh-see-boh)]

A substance containing no active drug, administered to a patient participating in a medical experiment as a control.

Note: Those receiving a placebo often get better, a phenomenon known as the placebo effect.

The American Heritage® New Dictionary of Cultural Literacy, Third Edition
Copyright © 2005 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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American Heritage Stedman's Medical Dictionary - Cite This Source - Share This

placebo pla·ce·bo (plə-sē'bō)
n. pl. pla·ce·bos or pla·ce·boes

A substance containing no medication and prescribed or given to reinforce a patient's expectation to get well.
An inactive substance or preparation used as a control in an experiment or test to determine the effectiveness of a medicinal drug.

Merriam-Webster's Medical Dictionary - Cite This Source - Share This
Main Entry: pla·ce·bo
Pronunciation: pl&-'sE-(")bO
Function: noun
Inflected Form: plural -bos
1 : a medicationprescribed more for the mental relief of the patient than for its actual effect on a disorder
2 : an inert or innocuous substance used especially in controlled experiments testingthe efficacy of another substance (as a drug)

Webster's Revised Unabridged Dictionary - Cite This Source - Share This

Placebo

Pla*ce"bo\, n. [L., I shall please, fut. of placere to please.]

1. (R. C. Ch.) The first antiphon of the vespers for the dead.

2. (Med.) A prescription intended to humor or satisfy.

To sing placebo, to agree with one in his opinion; to be complaisant to. --Chaucer.

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