Definition of fastness in English:

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Pronunciation: /ˈfas(t)nəs/


1A secure refuge, especially a place well protected by natural features: a remote Himalayan mountain fastness
More example sentences
  • Rommel's army had to be worn down, and if it had been allowed to withdraw intact into the mountain fastnesses of Tunisia, securing a decisive land victory in North Africa would have been rendered immensely difficult.
  • As, indeed, did the original inhabitants of the Cinque Terre: even after they moved downhill from their mountain fastnesses, most locals continued to work the land.
  • She describes the remote mountain fastnesses between Afghanistan and Pakistan and tells the tragic tale of a runaway young bride bought as a wife for a tribal man.
2The ability of a material or dye to maintain its color without fading or washing away: the dyes differ in their fastness to light
More example sentences
  • Moreover, the sizing does not impact the hand of the fabric or the wash fastness of garments, the company reported.
  • Many of the colors were not fast, although there is not agreement in the literature on fastness properties of the various dyes.


Old English fæstnes (see fast1, -ness).

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Syllabification: fast·ness

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