[fahy-bruh-ley-shuh n, or especially for 2, fib-ruh-]


the formation of fibrils.
Pathology. uncontrolled twitching or quivering of muscular fibrils.

Origin of fibrillation

First recorded in 1830–40; fibrillate + -ion Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for fibrillation

Historical Examples of fibrillation

British Dictionary definitions for fibrillation



a local and uncontrollable twitching of muscle fibres, esp of the heart, not affecting the entire muscle. Atrial fibrillation results in rapid and irregular heart and pulse rate. In ventricular fibrillation, the heart stops beating
irregular twitchings of the muscular wall of the heart, often interfering with the normal rhythmic contractions
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for fibrillation

c.1840, noun of action from fibrillate.

Online Etymology Dictionary, © 2010 Douglas Harper

fibrillation in Medicine


[fĭb′rə-lāshən, fī′brə-]


Fine, rapid twitching of individual muscle fibers with little or no movement of the muscle as a whole.
The formation of fibrils.
Vermicular twitching, usually slow, of individual muscular fibers, commonly occurring in the atria or ventricles of the heart and in recently denervated skeletal muscle fibers.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

fibrillation in Science



A rapid twitching of muscle fibers, as of the heart, that is caused by the abnormal discharge of electrical nerve impulses. Ventricular fibrillation is life-threatening.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.