fiber

US: /ˈfaɪbɚ/ ,(fī′bər)

WordReference Random House Learner's Dictionary of American English © 2025

fi•ber /ˈfaɪbɚ/   n. 

1. Textiles [countable] a fine, threadlike piece, such as of cotton.
2. matter or material made up of small thin threadlike pieces:
   [uncountable] mats made of cotton fiber.
   [countable] plastic fibers.
3. an essential or basic character, quality, or strength:
   [uncountable] people of strong moral fiber.
4. Biology a thin, threadlike, or long cell or structure in the body that is combined in a bundle of tissue:
   [countable] nerve fibers.
5. Nutrition Also called bulk, roughage.parts of plants that are hard or impossible to digest, eaten to aid the movement of food through the intestines:
   [uncountable] a diet rich in fiber.

Also,[esp. Brit.,] ˈfi•bre. 

WordReference Random House Unabridged Dictionary of American English © 2025

fi•ber  (fī′bər), n. 

1. Textiles a fine, threadlike piece, as of cotton, jute, or asbestos.
2. a slender filament:
   a fiber of platinum.
3. filaments collectively.
4. matter or material composed of filaments:
   a plastic fiber.
5. something resembling a filament.
6. an essential character, quality, or strength:
   people of strong moral fiber.
7. [Bot.]
   • Textiles filamentous matter from the bast tissue or other parts of plants, used for industrial purposes.
   • Botany a slender, threadlike root of a plant.
   • Botany a slender, tapered cell which, with like cells, serves to strengthen tissue.
8. Anatomy, Zoology a slender, threadlike element or cell, as of nerve, muscle, or connective tissue.
9. 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.
10. Chemistry See vulcanized fiber. 
11. Optics See optical fiber. 

Also,[esp. Brit.,] fibre. 

• Latin fibra filament
• Middle French)
• 1350–1400; 1970–75 for def. 9; Middle English fibre (

fi′ber•less, adj. 

Collins Concise English Dictionary © HarperCollins Publishers::

fiber / ˈfaɪbə/ noun

1. the usual US spelling of fibre

WordReference Random House Unabridged Dictionary of American English © 2025

fi•bre  (fī′bər), n. [Chiefly Brit.]

1. British Terms fiber.

Collins Concise English Dictionary © HarperCollins Publishers::

fibre, fiber / ˈfaɪbə/ noun

1. a natural or synthetic filament that may be spun into yarn, such as cotton or nylon
2. cloth or other material made from such yarn
3. a long fine continuous thread or filament
4. the structure of any material or substance made of or as if of fibres; texture
5. essential substance or nature
6. strength of character (esp in the phrase moral fibre)
7. See dietary fibre
8. a narrow elongated thick-walled cell: a constituent of sclerenchyma tissue
9. a very small root or twig

Etymology: 14th Century: from Latin fibra filament, entrails

ˈfibred, ˈfibered adjective