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.
This deadly strain of bird flu has already decimated wild bird and mammal populations worldwide.
From Science Daily ● Aug. 24, 2026
And catching bird flu can push our most threatened species, such as the orange-bellied parrot, to the brink of extinction.
From Science Daily ● Aug. 24, 2026
Moderna recently won approval for its mRNA-based flu vaccine, though analysts said this was more likely to be a long-term growth driver than an immediate financial windfall.
From The Wall Street Journal ● Aug. 19, 2026
It said the patient, Samantha, had booked a flu jab but was instead given a Covid vaccine after staff failed to show her a BSL video which would have highlighted the error.
From BBC ● Aug. 19, 2026
“Are you trying to give us all avian flu? Put that down! Throw it away! And—take a shower, for Pete’s sake!”
From "Liar & Spy" by Rebecca Stead
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.
