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.
Emily Hilliard, an HHS spokesperson, said Covid-19 doesn’t follow the same seasonal pattern as flu and other respiratory viruses.
From The Wall Street Journal ● Sep. 16, 2026
The respiratory virus season — which starts in the fall and ends in early spring — is expected to include the circulation of flu, COVID-19 and RSV.
From Salon ● Sep. 12, 2026
The scientific research in those cases involved work around the mosquito-born chikungunya virus, a "highly-pathogenic" strain of the bird flu, a family of viruses that include smallpox and mpox, venoms and other toxins.
From Barron's ● Sep. 11, 2026
The horses that pulled them potentially carried the equine flu from cities to farms and small towns.
From The Wall Street Journal ● Sep. 7, 2026
“Spanish flu claims one hundred thousand lives; Americans urged to wear masks, keep safe distance.”
From "The Brightwood Code" by Monica Hesse
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.
