What does fibrillate mean?
Fibrillate is a verb used chiefly in medicine to describe what happens when muscle fibers — most critically those of the heart — contract rapidly, irregularly, and out of sync with one another. Instead of producing an effective coordinated beat, the affected tissue simply quivers: atrial fibrillation, the most common sustained heart-rhythm disorder, is the classic example. The word derives from Latin fibra, meaning 'fiber,' via the diminutive fibrilla, so it literally evokes tiny threads twitching independently. Because it names a pathological state, fibrillate carries clinical rather than emotional connotations; it belongs to the vocabulary of cardiologists, nurses, and physiology texts, and it also underlies the familiar terms defibrillate and defibrillator. Figurative or lay uses are rare, making it a precise, technical term worth recognizing whenever heart-rhythm abnormalities are discussed.
verbTo fibrillate is to undergo rapid, irregular, uncoordinated twitching of muscle fibers, especially of the heart's atria or ventricles, as occurs in cardiac arrhythmias.
- (of muscle tissue, especially cardiac muscle) to contract rapidly, irregularly, and uncontrollably instead of in a coordinated beat
- (by extension, rare) to tremble or quiver rapidly like such twitching fibers
"The cardiologist watched the monitor as the patient's atria began to fibrillate."
"Surgeons restored a normal rhythm after the atrium continued to fibrillate for several minutes."
"Under the microscope, the isolated muscle fibers would fibrillate when exposed to the stimulant."
When a heart fibrillates, its chambers stop beating and merely quiver — which is why the word for 'tiny fiber' ended up describing one of medicine's most urgent emergencies.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of fibrillate
Fibrillate traces back to the Latin noun fibra, meaning 'fiber' or 'filament,' through the New Latin diminutive fibrilla, 'little fiber.' The verb was adopted into English in the nineteenth century as physiologists sought precise language for the fine, uncoordinated muscular twitching they observed, particularly in cardiac tissue. Its relatives include fibril and fibrillation, and its modern prominence owes much to the development of defibrillation, whose name borrows the same root.
Related word forms
How fibrillate is actually used
Almost exclusively medical or scientific in register; it appears in cardiology reports, textbooks, and clinical discussion rather than everyday conversation. It is typically used intransitively ('the atria fibrillated') though passive constructions are common in clinical writing.
Easily confused with fibrillate
Vibration is a rapid but regular back-and-forth motion, whereas fibrillation is rapid, random, and uncoordinated twitching of muscle fibers.
Oscillate means to swing rhythmically and predictably between two points, while fibrillate describes erratic, disorganized quivering with no regular pattern.