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
So why is backyard bird feeding such a problem when it comes to bird flu?
From Science Daily ● Aug. 24, 2026
The Food and Drug Administration has approved Moderna’s mRNA vaccines for the flu and RSV as well.
From The Wall Street Journal ● Aug. 19, 2026
Jaafri's probable cause of death was given by the hospital and medical examiner as bronchopneumonia due to flu and frailty.
From BBC ● Aug. 18, 2026
“My cousin got the stomach flu last week. That can come on real sudden.”
From "The Lions of Little Rock" by Kristin Levine
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.
