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

In adults ages 65 and older, the shot was 27.4% more effective than the standard flu vaccine. —Annika Kim Constantino, CNBC, 30 June 2025

What do people need to know about the flu vaccine and this ingredient? DR. —CBS News, 29 June 2025

These days, most people receive single-dose flu vaccines, Russo says. —Emily Kay Votruba, EverydayHealth.com, 27 June 2025

Be prepared for keto flu: Understand that temporary side effects like fatigue or brain fog may occur as your body adjusts to burning fat for fuel.12 Experiment with alternatives: Replace some high-carb favorites with low-carb alternatives like cauliflower rice, zucchini noodles, or almond flour. —Jamie Johnson, Verywell Health, 27 June 2025

Word History

Etymology

by shortening

First Known Use

1839, in the meaning defined at sense 1

Phrases Containing flu

• anti-flu
• Asian 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