fibrillation

noun

fi·​bril·​la·​tion ˌfi-brə-ˈlā-shən How to pronounce fibrillation (audio) ˌfī- How to pronounce fibrillation (audio)
1
: an act or process of forming fibers or fibrils
2
a
: a muscular twitching involving individual muscle fibers acting without coordination
b
: very rapid irregular contractions of the muscle fibers of the heart resulting in a lack of synchronism between heartbeat and pulse

Examples of fibrillation in a Sentence

Recent Examples on the Web
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Those exposed to the brightest light also had a 47% greater risk of having a heart attack and a 32% higher risk of developing atrial fibrillation. Kristen Rogers, CNN Money, 27 Oct. 2025 Six days later, on February 18, Gene’s death is believed to have occurred when his pacemaker recorded an episode of atrial fibrillation. Joy Williams, Harpers Magazine, 24 Oct. 2025 According to the American Heart Association, CKM syndrome can lead to atrial fibrillation, coronary heart disease, disability, kidney failure, peripheral artery disease, stroke, heart failure and even early death. Rachael O'Connor, MSNBC Newsweek, 21 Oct. 2025 When he was diagnosed with atrial fibrillation, Cuban used AI to track his medications and his workouts. Marco Quiroz-Gutierrez, Fortune, 2 Oct. 2025 See All Example Sentences for fibrillation

Word History

First Known Use

1845, in the meaning defined at sense 1

Time Traveler
The first known use of fibrillation was in 1845

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Cite this Entry

“Fibrillation.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/fibrillation. Accessed 28 Oct. 2025.

Medical Definition

fibrillation

noun
fi·​bril·​la·​tion ˌfib-rə-ˈlā-shən How to pronounce fibrillation (audio) ˌfīb- How to pronounce fibrillation (audio)
1
: an act or process of forming fibers or fibrils
2
a
: a muscular twitching involving individual muscle fibers acting without coordination
b
: very rapid irregular contractions of the muscle fibers of the heart resulting in a lack of synchronism between heartbeat and pulse see atrial fibrillation, ventricular fibrillation

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