fibrillation

noun

1. (countable, uncountable)The rapid, irregular, and unsynchronized contraction of the muscle fibers of the heart.

   “Though occasionally a “flatliner” can be revived with a defib, it is most commonly used to change the uncoordinated contractions of the heart (fibrillation) into a normal sinus rhythm—that is, to defibrillate the heart.”

   “The most common type of irregular heartbeat is atrial fibrillation or AFib. It is estimated that between three and six million people in the United States have AFib.”