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.
A total of 12 cases of H5 bird flu have been confirmed in Australia since June but all of them were in migratory sea birds, not local wildlife.
From Barron's • Jul. 10, 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
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
The move came two months after Defense Secretary Pete Hegseth ended the annual flu vaccine requirement for all military personnel.
From The Wall Street Journal • Jul. 2, 2026
Many of the soldiers from Camp Funston had a rough boat ride overseas and are still feeling indisposed with flu symptoms.
From "Moon Over Manifest" by Clare Vanderpool
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.
