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

These vaccines — which include immunizations for hepatitis A, hepatitis B, COVID-19 and the flu — are now only recommended for children at high risk of serious illness, which runs contrary to guidance from the American Academy of Pediatrics. —Keri Heath, Austin American Statesman, 27 Feb. 2026

Symptoms of foodborne illness usually include vomiting, diarrhea, abdominal pain, and flu-like symptoms such as fever, headache, and body aches. —Michele Laufik, Martha Stewart, 26 Feb. 2026

The increasing number of outbreaks of avian flu on US farms has made eggs an expensive - and rare - commodity. —Alex Harring, CNBC, 26 Feb. 2026

Here's what Means said on measles and flu vaccines. —Nicole Fallert, USA Today, 26 Feb. 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