a rapid, uncoordinated series of contractions of a muscle; esp., such contractions of some portion of the heart muscle, causing irregular heartbeats and sometimes ineffectual pumping of blood
Origin:
< fibril + -ation
See fibrillation in American Heritage Dictionary 4
noun
The forming of fibers.
a. Fine, rapid twitching of individual muscle fibers with little or no movement of the muscle as a whole.
b. Rapid uncoordinated twitching movements that replace the normal rhythmic contraction of the heart and may cause a lack of circulation and pulse.