fibrillation

(fĭbˌrə-lāˈshən, fīˌbrə-)

1. The forming of fibers.
2. 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.