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

Moderna’s mRNA flu vaccine requires less time between strain selection and public circulation, which could allow for a closer match between the immunity conferred by vaccines and the season’s circulating influenza strains. — Elise Haulund, CNN Money, 6 Aug. 2026

Even though mFlusiva outperformed the traditional flu shot in a late-stage clinical trial, its approval was not a sure thing. — Berkeley Lovelace Jr, NBC news, 6 Aug. 2026

The approval covers two of the most vulnerable populations for flu—adults aged 50 to 65 and adults aged 65 and up—on the condition that Moderna will run a further clinical trial in the older group. — Claire Cameron, Scientific American, 6 Aug. 2026

Health experts say the shot, made by Moderna, could have several advantages over traditional flu vaccines, but its approval comes at a time when federal health agencies have walked back recommending flu vaccines for many people. — Alice Park, Time, 6 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