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

For example, clinicians choosing an anticoagulant for a patient with atrial fibrillation and stage three kidney disease often need to consult separate cardiology and nephrology guidelines, since the two aren’t typically integrated. — Garth Friesen, Forbes.com, 25 July 2026

It’s also associated with a lower likelihood of developing a long list of conditions, including heart disease, stroke, heart failure, atrial fibrillation, high blood pressure and Type 2 diabetes. — Anahad O’Connor, Washington Post, 21 July 2026

Researchers did observe higher rates of certain conditions, including atrial fibrillation, acute kidney injury and pulmonary embolism, underscoring the need for careful patient selection and monitoring. — Annika Kim Constantino, CNBC, 20 July 2026

However, that study also found a higher incidence of acute kidney injury, atrial fibrillation, and pulmonary embolism in those taking testosterone replacement therapy. — Alexander P. Cole, STAT, 18 July 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