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[fahy-bruh-ley-shuh n, or especially for 2, fib-ruh-] /ˌfaɪ brəˈleɪ ʃən, or especially for 2, ˌfɪb rə-/
the formation of fibrils.
Pathology. uncontrolled twitching or quivering of muscular fibrils.
Origin of fibrillation
1830-40; fibrillate + -ion Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the web for fibrillation
  • In atrial fibrillation, the atrium or upper chamber of the heart does not beat an organized manner.
  • Slayton had atrial fibrillation, which had never been debilitating, but the flight surgeons grounded him anyway.
  • The surgical tool has performed well in animal tests designed to mimic a disorder called atrial fibrillation.
  • All things being equal, atrial fibrillation is a relatively benign condition as long as it can be controlled.
  • It is used to treat some forms of irregular heartbeat, such as atrial fibrillation.
  • But coming at a time when the euro area is in fibrillation, the opinion of an external expert is bound to draw some attention.
  • Atrial fibrillation is a major risk factor for arterial embolism.
  • Digoxin, calcium channel blockers, and beta blockers may be used with caution in patients with atrial fibrillation.
  • Patients with previous heart attacks or with arrhythmias, such as atrial fibrillation, are at risk for this problem.
  • If the arrhythmia is due to atrial fibrillation, blood thinners will also be used to reduce the risk of blood clots.
British Dictionary definitions for fibrillation


/ˌfaɪbrɪˈleɪʃən; ˌfɪb-/
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
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Word Origin and History for fibrillation

c.1840, noun of action from fibrillate.

Online Etymology Dictionary, © 2010 Douglas Harper
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fibrillation in Medicine

fibrillation fib·ril·la·tion (fĭb'rə-lā'shən, fī'brə-)

  1. Fine, rapid twitching of individual muscle fibers with little or no movement of the muscle as a whole.

  2. The formation of fibrils.

  3. 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.
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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 © 2002. Published by Houghton Mifflin. All rights reserved.
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