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

Although the autumn respiratory illness season hasn’t kicked off, and flu and RSV activity remain low, there’s a growing summer wave of Covid-19. — Jen Christensen, CNN Money, 20 Aug. 2026

Ryan doesn’t get the seasonal flu shot and has never been immunized against Covid-19. — Felice J. Freyer, STAT, 19 Aug. 2026

Many of these are similar to those of the flu, pneumonia or the common cold. — Hali Smith, Idaho Statesman, 19 Aug. 2026

The bacteria can cause flu-like symptoms such as fever, vomiting, stomach cramps and diarrhea. — Cara Lynn Shultz, PEOPLE, 19 Aug. 2026

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
• stomach flu
• 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