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

Understanding how cardiac neurons function could lead to new therapies for a range of cardiovascular conditions, such as atrial fibrillation, heart failure, and myocardial infarctions. — Isabella Backman, Hartford Courant, 14 Aug. 2026

This utopic view of college reflects Linklater’s own experiences playing centerfield at Sam Houston State University before a diagnosis of atrial fibrillation cut short his athletic career and pushed him into the humanities. — Vikram Murthi, IndieWire, 11 Aug. 2026

Adherence is often low, and untreated sleep apnea can worsen hypertension, atrial fibrillation and the daytime sleepiness. — Jesse M. Pines, Forbes.com, 10 Aug. 2026

After about 30 seconds, a connected smartphone app analyzes the reading for signs of an irregular heart rhythm, including possible atrial fibrillation. — Kurt Knutsson, FOXNews.com, 7 Aug. 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