n.
Pronunciation: ˌ fi-br ə - ' l ā -sh ə n, ˌ f ī -
Function: noun
Date: 1845
1 : an act or process of forming fibers or fibrils
2 a : a muscular twitching involving individual muscle fibers acting without coordination b : very rapid irregular contractions of the muscle fibers of the heart resulting in a lack of synchronism between heartbeat and pulse