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.
Becerra pointed to his experiences leading the sprawling federal health agency in the Biden administration, including dealing with the COVID-19 pandemic, the wildfires that devastated Maui, Hawaii, avian flu and monkey pox.
From Los Angeles Times • Apr. 1, 2026
Egg prices had reached record highs a year ago as bird flu caused a sharp drop in supply.
From MarketWatch • Apr. 1, 2026
"It is certainly not as infective as say flu or COVID-19, and requires often fairly prolonged close contact before transmission takes place," said Andrew Lee, Professor of Public Health at the University of Sheffield.
From Barron's • Mar. 19, 2026
His illness began with the flu, which quickly worsened and was complicated by bacterial pneumonia.
From Science Daily • Mar. 18, 2026
He heard what Mosley was saying, but the fact remained: no flu, no mom staying home, no getting fired.
From "The First State of Being" by Erin Entrada Kelly
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.
