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.
Moderna’s revenue rose 29% to $1.3 billion in the third quarter, which is usually the company’s highest-revenue quarter based on the seasonality of COVID, RSV and flu vaccines.
From MarketWatch ● Nov. 6, 2026
Sir Tom Jones has told fans he feared his life was "over" after being admitted to hospital in the US with flu.
From BBC ● Nov. 5, 2026
A small group of these nurses were eventually allowed to treat Black soldiers in the US Army struck down by Spanish flu.
From Barron's ● Nov. 1, 2026
In early October, for example, Talarico took a brief hiatus from the campaign trail to recover from a severe case of the flu.
From Salon ● Oct. 31, 2026
He thought about how she’d been fired because he’d had the flu.
From "The First State of Being" by Erin Entrada Kelly
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Get a wordDefinitions 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.
