prophylactic
Americanadjective
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defending or protecting from disease or infection, as a drug.
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preventive or protective.
noun
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Medicine/Medical. a prophylactic medicine or measure.
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a preventive.
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a device, usually a rubber sheath, used to prevent conception or venereal infection; condom.
adjective
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protecting from or preventing disease
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protective or preventive
noun
Other Word Forms
Derived Forms
Etymology
Origin of prophylactic
First recorded in 1565–75; from Greek prophylaktikós “of guarding,” equivalent to prophylak- (base of prophylássein “to guard beforehand”) + -tikos -tic; see prophylaxis
Explanation
Prophylactic might sound like a prehistoric period when dinosaurs roamed the earth, but it actually describes something that can prevent something negative, such as disease. Prophylactic surgery to remove a mole can prevent skin cancer. If you want to avoid getting sick, you can get a vaccine, take medicine, or have surgery — all of which are considered prophylactic measures. Delve deeper into the history of this four-syllable word and you'll find the Greek term prophulaktikos, which means to "guard before." Prophylactic can also describe a contraceptive used to prevent pregnancy. This use of the word started because condoms, which are prophylactics, were originally designed to prevent disease, not pregnancy.
Vocabulary lists containing prophylactic
Ruth Bader Ginsburg (1933–2020) Tribute List
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The Gene
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Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
Pet owners across the country have been advised they should treat their cats and dogs as a preventative measure every month, known as prophylactic use - although many veterinary organisations have now updated their advice.
From BBC • Jun. 10, 2026
In the past few years, he’s seen a notable change in 20-somethings coming into his office, both with cancer as well as for prophylactic surgeries, including Benson’s.
From The Wall Street Journal • Jun. 7, 2026
Volunteers were divided into two groups: prophylactic arm and therapeutic arm.
From Science Daily • Feb. 19, 2026
It also announced plans to buy Cidara Therapeutics, which is working on antiviral treatments, including a flu prophylactic in Phase 3, for $9.2 billion.
From MarketWatch • Feb. 3, 2026
As a prophylactic against innumerable diseases, we have recommended the use of the Anglo-Turkish Bath.
From Turkish and Other Baths A Guide to Good Health and Longevity by Stables, Gordon
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
