[ fahy-ber ]
See synonyms for fiber on
  1. a fine, threadlike piece, as of cotton, jute, or asbestos.

  2. a slender filament: a fiber of platinum.

  1. filaments collectively.

  2. matter or material composed of filaments: a plastic fiber.

  3. something resembling a filament.

  4. an essential character, quality, or strength: people of strong moral fiber.

  5. Botany.

    • filamentous matter from the bast tissue or other parts of plants, used for industrial purposes.

    • a slender, threadlike root of a plant.

    • a slender, tapered cell which, with like cells, serves to strengthen tissue.

  6. Anatomy, Zoology. a slender, threadlike element or cell, as of nerve, muscle, or connective tissue.

  7. Nutrition.Also called bulk, dietary fiber, roughage.

    • the structural part of plants and plant products that consists of carbohydrates, as cellulose and pectin, that are wholly or partially indigestible and when eaten stimulate peristalsis in the intestine.

    • food containing a high amount of such carbohydrates, as whole grains, fruits, and vegetables.

  8. Chemistry. vulcanized fiber.

  9. Optics. optical fiber.

Origin of fiber

1350–1400; 1970–75 for def. 9; Middle English fibre (<Middle French ) <Latin fibra filament
  • Also especially British, fi·bre .

Other words from fiber

  • fi·ber·less, adjective
  • in·ter·fi·ber, adjective

Words Nearby fiber Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use fiber in a sentence

British Dictionary definitions for fiber


/ (ˈfaɪbə) /

  1. the usual US spelling of fibre

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Scientific definitions for fiber


[ bər ]

  1. The parts of grains, fruits, and vegetables that contain cellulose and are not digested by the body. Fiber helps the intestines absorb water, which increases the bulk of the stool and causes it to move more quickly through the colon.

  2. One of the elongated, thick-walled cells, often occurring in bundles, that give strength and support to tissue in vascular plants. Fibers are one type of sclerenchyma cell.

  1. Any of the elongated cells of skeletal or cardiac muscle, made up of slender threadlike structures called myofibrils.

  2. The axon of a neuron.

Other words from fiber

  • fibrous adjective

The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.