fibrillation

noun

fi·​bril·​la·​tion ˌfi-brə-ˈlā-shən  ˌfī- 

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

World-first findings on coffee and irregular heartbeat University of Adelaide and University of California, San Francisco (UCSF) researchers led a randomized clinical trial of 200 adults from Australia, the US and Canada with atrial fibrillation (AF) to test coffee's impact on irregular heartbeats. —New Atlas, 2 Jan. 2026

Untreated atrial fibrillation can lead to heart failure after a long period of time. —Angelica Stabile, FOXNews.com, 16 Dec. 2025

Fetterman, who has been open about his mental and physical health struggles, recently fell due to a ventricular fibrillation flare-up while on a walk in Pennsylvania. —Molly Parks, The Washington Examiner, 19 Nov. 2025

Ventricular fibrillation is a type of irregular heartbeat. —CBS News, 16 Nov. 2025

Word History

First Known Use

1845, in the meaning defined at sense 1

Rhymes for fibrillation

• abdication
• aberration
• abjuration
• abnegation
• abrogation
• acceptation
• acclamation
• acclimation
• accusation
• activation
• actuation
• acylation

Medical Definition

fibrillation

noun

fi·​bril·​la·​tion ˌfib-rə-ˈlā-shən  ˌfīb- 

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