brain fog

noun

: a usually temporary state of diminished mental capacity marked by inability to concentrate or to think or reason clearly

Examples of brain fog in a Sentence

Recent Examples on the Web

The one who fights brain fog and exhaustion all day? —Alyce Collins, MSNBC Newsweek, 19 Sep. 2025

Those included headaches, insomnia, light and noise sensitivity, brain fog, anxiety, confusion, joint pain, disordered eating, nausea and weight loss and gain. —Emily Blackwood, PEOPLE, 18 Sep. 2025

Dehydration can cause fatigue and brain fog. —Bryan Robinson, Forbes.com, 16 Sep. 2025

Prior to the 2024 incident, Mangione reportedly shared information on Reddit about a number of health issues, including struggles with back pain, brain fog, and twitching leg muscles. —Olivia-Anne Cleary, Time, 16 Sep. 2025

Word History

First Known Use

1853, in the meaning defined above

Rhymes for brain fog

• agog
• backlog
• bulldog
• bullfrog
• eclogue
• eggnog
• groundhog
• hedgehog
• leapfrog
• prolog
• sheepdog
• watchdog

Medical Definition

brain fog

noun

: a usually temporary state of diminished mental capacity marked by inability to concentrate or to think or reason clearly

This brain fog can be a result of being overly stressed, tired, carrying extra weight, consuming too many calories or consistently consuming a diet poor in nutrients.

—Kylie Helgens, The Gazette (Cedar Rapids, Iowa)