one of the delicate, threadlike portions of which the tissues of plants and animals are in part constituted; as, the fiber of flax or of muscle.-any fine, slender thread, or threadlike substance; as, a fiber of spun glass; especially, one of the slender rootlets of a plant.-sinew; strength; toughness; as, a man of real fiber.-a general name for the raw material, such as cotton, flax, hemp, etc., used in textile manufactures.