1) Jerk 2) Twitch 
1. To make or to become fibrillar. ... Synonym: fibrillated. ... 3. To be in a state of fibrillation. ... (05 Mar 2000) ... 
Type: Term Pronunciation: fi′bri-lāt Definitions: 1. To make or to become fibrillar. 2. To be in a state of fibrillation (3). Synonyms: fibrillated
[v] - make fine, irregular, rapid twitching movements, as of muscles
fibrillate 1. To make or to become fibrillar. 2. To be in a state of fibrillation. 3. To make fine, irregular, rapid twitching movements. 4. To undergo rapid irregular beating or uncontrolled contraction, or to make the heart or muscles undergo these activities.
verb make fine, irregular, rapid twitching movements; `His heart fibrillated and he died`