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

Elderberries have a rich history in traditional medicine, particularly for relieving cold and flu symptoms. —Morgan Pearson, Verywell Health, 12 Dec. 2025

Liam — who had a high fever of 102° and an elevated heart rate — tested negative for RSV, the flu, and Covid-19, but his condition quickly began to decline. —Cara Lynn Shultz, PEOPLE, 11 Dec. 2025

Topiel says the spike in flu cases could also be because fewer people are getting vaccinated — and this year's influenza vaccine isn't as protective as years past, but it's still recommended. —Stephanie Stahl, CBS News, 11 Dec. 2025

No, though some call it the stomach flu, norovirus is not related to the flu or influenza, the CDC said. —Jenna Prestininzi, Freep.com, 11 Dec. 2025

Word History

Etymology

by shortening

First Known Use

1839, in the meaning defined at sense 1

Phrases Containing flu

• anti-flu
• Asian flu
• avian 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