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.
"Watching these tiny organelles in the nucleus dissolve, consistently across every cell line and every flu strain we tested, told us this isn't a side effect of infection -- it might be a strategy,"
From Science Daily ● Jul. 21, 2026
Scientists have detected the highly contagious H5 bird flu in an Australian seabird for the first time, the government said Friday.
From Barron's ● Jul. 10, 2026
Gannet populations at two of the world's largest colonies are not expected to recover from the impact of 2022's bird flu outbreak for almost two decades.
From BBC ● Jul. 3, 2026
The affected data include childhood immunization rates against diphtheria, tetanus, pertussis, polio, measles, mumps and rubella, hepatitis, chicken pox and flu; and rates for 13 year olds and expectant mothers.
From Los Angeles Times ● Jul. 3, 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.
