/ˈfībrəl/
Noun, pl. fibrils
1. A fine fiber, such as a myofibril or neurofibril. (wikipedia.org)
2. A fine fibre or filament. (wiktionary.org)
3. (Biology)
Any fine, filamentous structure in animals or plants. (wiktionary.org)
4. A small or slender fiber. (Google Dictionary)
5. The diminuitive of fibre. A small fibre, a fine thread. (biology-online.org)
Word origin: 1680s, back-formation from Modern Latin fibrilla, diminutive of Latin fibra.