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

How closely matched the flu vaccine is to the dominant strain of the season is part of what accounts for the year-to-year changes in the shot’s effectiveness. — Elise Haulund, CNN Money, 14 Aug. 2026

The blogger was hospitalized in March after taking flu medicine on an empty stomach, which later led him to develop an ulcer, perforation and sepsis. — Kevin Dolak, HollywoodReporter, 13 Aug. 2026

The vaccine was shown to be almost 27% more effective against the flu than the standard flu shot. — Devika Rao, TheWeek, 13 Aug. 2026

Nearly 82% said ensuring flu shots are available, accessible, and affordable was a priority. — Samantha-Jo Roth, The Washington Examiner, 13 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