(countable) A single piece of a given material, elongated and roughly round in cross-section, often twisted with other fibres to form thread.

(uncountable) Material in the form of fibres.

Dietary fibre.

Moral strength and resolve.

(mathematics) The preimage of a given point in the range of a map.

(category theory) Said to be of a morphism over a global element: The pullback of the said morphism along the said global element.

(computing) A kind of lightweight thread of execution.

(cytology) A long tubular cell found in bodily tissue.