Fibrillation
WordNet
noun
(1) Act or process of forming fibrils
(2) Muscular twitching involving individual muscle fibers acting without coordination
WiktionaryText
Etymology
From fibrilla, diminutive of fibra, "fiber," in reference to the muscle strands of the heart.
Noun
- The rapid, irregular, and unsynchronized contraction of the muscle fibers of the heart.