# fibrillation

/ˌfɪbɹɪˈɫeɪʃən/ (US) · /fˌɪbɹɪlˈeɪʃən/ (UK) · CEFR C1 · Noun

Source: https://englishreference.com/word/fibrillation
Updated: 2026-05-20

## Definition

a fast, irregular, and uncontrolled beating of the heart. It is a serious medical condition that can be life-threatening if not treated quickly.

For teachers: a rapid, irregular, and uncoordinated contraction of the heart muscle, typically occurring in the atria or ventricles. It is a serious arrhythmia that can lead to cardiac arrest if not corrected.

## Examples

- The doctor checked for signs of heart fibrillation.
- Emergency responders used a defibrillator to restore a normal heart rhythm after the patient suffered from ventricular fibrillation.
- While atrial fibrillation is more common and often manageable with medication, ventricular fibrillation is a medical emergency that requires immediate electrical intervention to prevent sudden cardiac death.

---

From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.