• (n.) A minute thread of fiber, as one of the fibrous elements of a muscular fiber; a fibril.
Fi·bril'la noun ; plural FibrillÆ . [ New Latin See Fibril .] A minute thread or fiber, as one of the fibrous elements of a muscular fiber; a fibril. 
Type: Term Pronunciation: fī-bril′ă, -ē Synonyms: fibril
fibrilla (s), fibrillae (pl) A minute thread of fiber, as one of the fibrous elements of a muscular fiber; a fiber or fibers.