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

Bird flu, a highly contagious airborne respiratory virus, affects poultry — including chickens, ducks and turkeys — and some wild bird species, including geese and shorebirds, the department said. —Laura Fay, CBS News, 11 Jan. 2026

There may be more guys getting flu shots, and more willingness to sit out a day of practice when under the weather, but the era of masking and distancing is over. —Jacob Feldman, Sportico.com, 10 Jan. 2026

Back in December, Althea's flu symptoms worsened from a fever to dizziness and then a seizure, WHDH 7News reported. —Escher Walcott, PEOPLE, 10 Jan. 2026

Seasonal flu levels are above average and on the rise across most of the country. —Melissa Willets, Parents, 10 Jan. 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
• 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