fastness

noun

fast·​ness ˈfas(t)-nəs How to pronounce fastness (audio)
Synonyms of fastnessnext
1
: the quality or state of being fast: such as
a
: the quality or state of being fixed
b
: the quality or state of being swift
c
: colorfast quality
d
: resistance (as of an organism) to the action of a usually toxic substance
2
a
: a fortified or secure place
b
: a remote and secluded place
vacationed in their mountain fastness

Synonyms

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Examples of fastness in a Sentence

the amazing fastness with which the boy took his shower had us wondering if he'd used any water the guerillas retreated to their network of hidden fastnesses deep within the mountains
Recent Examples on the Web
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
Like the pressing, the hard work mentality and fastness of transition for example. — Andy Jones, New York Times, 29 May 2025 Editors and contributors compare dozens of sets and look for qualities such as softness, durability, breathability, color fastness, and how well the linens launder and withstand wear. — Yelena Moroz Alpert, Architectural Digest, 16 May 2025

Word History

First Known Use

before the 12th century, in the meaning defined at sense 1

Time Traveler
The first known use of fastness was before the 12th century

Rhymes for fastness

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Browse Nearby Words

fastnacht
fastness
Fast of Esther
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Cite this Entry

“Fastness.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/fastness. Accessed 13 Aug. 2025.

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Kids Definition

fastness

noun
fast·​ness ˈfas(t)-nəs How to pronounce fastness (audio)
1
: the quality or state of being fast
2
: a fortified or secure place

Medical Definition

fastness

noun
fast·​ness ˈfas(t)-nəs How to pronounce fastness (audio)
: resistance (as of an organism) to the action of a usually toxic substance
streptomycin fastness developed by a strain of tubercule bacillus
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