What does fibrillated mean?
Fibrillated describes something broken down or arranged into fine, thread-like fibers. Its most familiar use is medical: when heart muscle becomes fibrillated, it contracts in rapid, disorganized twitches rather than a single coordinated beat, producing the irregular rhythm known as fibrillation. The word also appears in technical fields such as papermaking and materials science, where fibers are deliberately split into finer filaments to improve bonding and strength. Derived from the Latin diminutive 'fibrilla', meaning a small fiber, the term belongs chiefly to formal, scientific registers and is rarely heard in casual conversation. Understanding it is useful both for interpreting medical diagnoses and for following discussions of industrial fiber processing.
Past tense and past participle of 'fibrillate': to develop rapid, irregular muscular contractions, or to break into fine fibers.
"The surgeon observed that the ventricles had fibrillated during the procedure."
In cardiology the intransitive use dominates; the transitive sense (to split something into fibers) occurs mainly in industrial contexts.
Composed of or divided into fine thread-like fibers; exhibiting irregular fibrillar structure or twitching.
"The fibrillated surface of the membrane improved filtration performance."
When your heart fibrillates, it fires hundreds of tiny contractions instead of one strong beat — the word literally describes muscle reduced to trembling threads.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of fibrillated
Fibrillated derives from 'fibrillate', built on the Latin 'fibrilla', a diminutive of 'fibra' meaning fiber. The term entered scientific English in the nineteenth century as physiologists described muscles breaking into fine, quivering filaments of contraction. It shares this root with 'fibril', 'fibrin', and 'fibre'.
Related word forms
How fibrillated is actually used
Most common in medical and technical writing. As an adjective it is often used predicatively ('the heart was fibrillated'), though clinical texts more often describe the rhythm itself as 'fibrillating' or refer to 'atrial fibrillation'. In materials science and papermaking, the term carries no pathological connotation and simply describes desirable fiber separation.
Easily confused with fibrillated
'Fabricated' means invented or manufactured, while 'fibrillated' refers to fibers splitting into fine strands or muscle quivering irregularly.