flu
Americannoun
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a specific variety of influenza, usually named for its point of dissemination or its animal vector.
Hong Kong flu; swine flu.
noun
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short for influenza
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any of various viral infections, esp a respiratory or intestinal infection
Etymology
Origin of flu
First recorded in 1830–40; shortened form
Compare meaning
How does flu compare to similar and commonly confused words? Explore the most common comparisons:
Explanation
The flu is a disease that's easily spread between people. When you have body aches, a fever, and a sore throat, you probably have the flu. The word flu is shorthand for "influenza," the official name of this infectious, viral illness. It's not unusual to get the flu, especially in the winter, and while it usually isn't serious, it can be deadly for some groups of people. Your chances of getting the flu are greatly reduced if you get a flu shot. The Italian root influenza means "influenza" or "epidemic," but also "visitation" or "influence of the stars."
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.
A clearer view of this takeover could help scientists develop more effective flu vaccines and antiviral drugs.
From Science Daily ● Jul. 21, 2026
A total of 12 cases of H5 bird flu have been confirmed in Australia since June but all of them were in migratory sea birds, not local wildlife.
From Barron's ● Jul. 10, 2026
Mary Holland, the chief executive of Children’s Health Defense, said Shaw had tried to warn her pediatrician about a family history of adverse reactions to the flu vaccine.
From The Wall Street Journal ● Jul. 8, 2026
The H5N1 bird flu virus was first identified in poultry in Asia in 1996 before spreading to wild bird populations around the world.
From BBC ● Jul. 3, 2026
Then Reb Saunders became ill, and at the same time my father also took to his bed with the flu, a severe case that bordered on pneumonia for a while and frightened me terribly.
From "The Chosen" by Chaim Potok
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.
