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

This diet has been shown to increase life expectancy and lower the risk of cardiovascular disease, type 2 diabetes, atrial fibrillation (irregular heartbeat), breast cancer, and more. —Isabel Vasquez Rd Ldn, Health, 13 Aug. 2025

Medical records reportedly revealed that Hogan was previously diagnosed with atrial fibrillation — a heart condition defined as having an irregular heart rhythm — and chronic lymphocytic leukemia, a form of cancer. —Larisha Paul, Rolling Stone, 31 July 2025

The cremation summary obtained by Deadline says the WWE icon had a history of atrial fibrillation, a condition characterized by an irregular heart rate, aka AFib. —Madeleine Marr, Miami Herald, 31 July 2025

Atrial fibrillation is an irregular heartbeat, also known as an arrhythmia. —Tom Gavin, EverydayHealth.com, 24 June 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