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
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
Somedays her brain fog, headaches and blood pressure would be so bad, her mom needed to pick her up from school. — Maggie Menderski, Louisville Courier Journal, 28 Aug. 2026 Cognitive symptoms, brain fog, memory problems, and difficulty finding words appear online nearly four times as often. — Yulin Hswen, STAT, 27 Aug. 2026 Pasadena Fire Captain Matt Caffey, also a paramedic for 28 years, helped fight last year’s Eaton fire in Southern California and said the smoke exposure from burning neighborhoods brings on coughing, vomiting and brain fog. — ABC News, 23 Aug. 2026 From anger to brain fog, these issues can seriously disrupt people’s lives. — Jennifer Fields, Washington Post, 23 Aug. 2026 See All Example Sentences for brain fog

Word History

First Known Use

1853, in the meaning defined above

Time Traveler
The first known use of brain fog was in 1853

Rhymes for brain fog

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Browse Nearby Words

brain-fever bird
brain fog
brain food
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Cite this Entry

“Brain fog.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/brain%20fog. Accessed 1 Sep. 2026.

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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)
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