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

The Hopkins team hopes to study the digital twin approach in a larger study with other hospitals, and has begun a trial using it to treat a more common type of irregular heartbeat called atrial fibrillation. —ABC News, 1 Apr. 2026

Researchers compared these timing groups with health data including rates of high blood pressure, obesity, high cholesterol, atrial fibrillation, coronary artery disease, and other cardiovascular health problems. —Tom Gavin, EverydayHealth.com, 20 Mar. 2026

Turned out that Self was dehydrated and got AFib (atrial fibrillation) during a brief hospital stay. —Shreyas Laddha, Kansas City Star, 10 Mar. 2026

These structural changes in the heart muscle increase the risk of arrhythmias, especially atrial fibrillation. —Valerie Cacho, Verywell Health, 26 Feb. 2026

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