flu

noun

ˈflü 

1

: influenza

2

: any of several virus diseases marked especially by respiratory or intestinal symptoms

flu-like

ˈflü-ˌlīk 

adjective

Examples of flu in a Sentence

He came down with a bad bout of the flu.

Recent Examples on the Web

The researchers concluded that the best way to predict a person’s response to an upcoming flu vaccine (containing the currently circulating flu strain) is to measure the person’s immune response to the flu vaccine strain used in past years. —Noah Lyons, San Diego Union-Tribune, 3 June 2025

Bird flu already has devastated the dairy and poultry industries in many regions and sickened dozens of farmworkers. —Michael Hiltzik, Los Angeles Times, 3 June 2025

The flu mutates about 34 times more frequently than Covid. —/ Cbs News, CBS News, 1 June 2025

Bird flu remains a major threat that will strike again—as long as factory farms continue to dominate our poultry market. —Mandy Taheri, MSNBC Newsweek, 31 May 2025

Word History

Etymology

by shortening

First Known Use

1839, in the meaning defined at sense 1

Phrases Containing flu

• anti-flu
• Asian flu
• bird flu
• blue flu
• flu season
• swine flu
• yuppie flu

Rhymes for flu

• blew
• blue
• boo
• brew
• chew
• chou
• clue
• coo
• coup
• crew
• cue
• dew

Kids Definition

flu

noun

ˈflü 

1

: influenza sense 1

2

: any of several virus diseases that are something like a cold

flu-like

ˈflü-ˌlīk

adjective

Medical Definition

flu

noun

ˈflü 

1

: influenza

2

: any of several chiefly viral illnesses marked especially by respiratory or gastrointestinal symptoms see intestinal flu

flu-like

-ˌlīk 

adjective

also flulike

flu-like symptoms