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

Influenza, more commonly known as the flu, can be more serious than the common cold and other illnesses, especially for kids with chronic conditions and those under 5 years old, the Centers for Disease and Prevention notes. — ABC News, 7 Oct. 2026

And people in other parts of the country should make arrangements to get their shots within the next two or three weeks, because booking appointments will get more challenging as flu activity starts to heat up elsewhere. — Amanda Erickson, STAT, 6 Oct. 2026

Unlike in previous years, the CDC has not launched a broad public campaign this fall urging Americans to get their flu shots, even as unusually early activity is emerging in parts of the West. — Lena H. Sun, Washington Post, 4 Oct. 2026

The usual symptoms include high fever, headache, stiffness and an overall feeling that resembles the flu. — David J. Neal, Miami Herald, 3 Oct. 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