a specific variety of influenza, usually named for its point of dissemination or its animal vector: Hong Kong flu; swine flu.

Origin of flu

First recorded in 1830–40; shortened form
Can be confusedflew flu flue
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for flu

Contemporary Examples of flu

Historical Examples of flu

  • Then he was taken down with the 'flu' and had to give up study.

    Galusha the Magnificent

    Joseph C. Lincoln

  • I wish some of those fellows with the flu could have you to look after them.


    Alice Hegan Rice

  • If he were on Earth, he would be certain it was the flu; in the Centaurus system, kranken.

    Bolden's Pets

    F. L. Wallace

  • If he hadn't gone with the flu, that ranch'd been paid for in another year.

    Polly and Eleanor

    Lillian Elizabeth Roy

  • "Was sure I was coming down with the flu," Clavering mumbled.

    Black Oxen

    Gertrude Franklin Horn Atherton

British Dictionary definitions for flu


noun informal

the flu short for influenza
any of various viral infections, esp a respiratory or intestinal infection
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for flu

1839, flue, shortening of influenza. Spelling flu attested from 1893. For choice of middle syllable, not a common method of shortening in English, Weekley compares tec for detective, scrip for subscription.

Online Etymology Dictionary, © 2010 Douglas Harper

flu in Medicine




The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

flu in Science



See influenza.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.