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 one, countless stories have surfaced of the Apple Watch proactively catching atrial fibrillation, an irregular heart rate, alerting someone to go to the hospital. —Alexa Mikhail, Flow Space, 24 Apr. 2026

The stroke was a result of atrial fibrillation, which he was diagnosed with in 2017. —Finch Walker, USA Today, 23 Apr. 2026

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, 22 Apr. 2026

New research from the University of Miami (UM) Miller School of Medicine could one day change the way people with atrial fibrillation are treated. —Cbs Miami Team, CBS News, 10 Apr. 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