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

Unlike the appendage, where atrial fibrillation is necessary for clots to form, stagnation and clot formation can occur within the LASP even in a perfectly normal heart rhythm. — Subramaniam C. Krishnan, STAT, 28 Sep. 2026

Richie recently underwent a heart procedure for atrial fibrillation and canceled some tour dates but is expected to begin a residency in Las Vegas next month. — Peter White, Deadline, 24 Sep. 2026

Among the younger adults who experienced strokes, there was an increase in hypertension, diabetes, atrial fibrillation (irregular heartbeat) and substance use. — Melissa Rudy, FOXNews.com, 24 Sep. 2026

These signs can be precursors to dysfunction and disease, per the researchers, including heart failure and atrial fibrillation (commonly known as AFib). — Mary Walrath-Holdridge, USA Today, 10 Sep. 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