fi·ber (fīˈbər)

1. A slender thread or filament.
2. Extracellular filamentous structures such as collagenic or elastic connective tissue fibers.
3. The nerve cell axon with its glial envelope.
4. An elongated threadlike cell, such as a muscle cell or one of the epithelial cells of the lens of the eye.
5. Coarse, indigestible plant matter, consisting primarily of polysaccharides such as cellulose, that when eaten stimulates intestinal peristalsis. Also called roughage.