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

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

Ventricular fibrillation, also known as V-fib, is an abnormal heart rhythm (arrhythmia) that causes a person's lower heart chambers to race and affects their ability to pump blood, according to the Cleveland Clinic. —Terry Collins, USA Today, 13 Nov. 2025

Atrial fibrillation can cause blood to pool in a chamber of the heart, increasing the risk of clot formation. —Gabe Whisnant, MSNBC Newsweek, 13 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