1
as in speed
a high rate of movement or performance
the amazing fastness with which the boy took his shower had us wondering if he'd used any water
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Antonyms & Near Antonyms
2
as in stronghold
a structure or place from which one can resist attack
the guerillas retreated to their network of hidden fastnesses deep within the mountains
Synonyms & Similar Words
3
as in loyalty
adherence to something to which one is bound by a pledge or duty
his uncompromising fastness to the cause of freedom was beyond question
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Antonyms & Near Antonyms
Example Sentences
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Recent Examples of fastness
Li said the color builds the familiar ring-dye, white-core look designers expect, then fades predictably in laundry while maintaining high light fastness (Grade 4–5) and strong anti-yellowing.
—
Angela Velasquez, Sourcing Journal, 11 Nov. 2025
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
The Neutral Ground had cowboys (or Cow Boys), Indians, cavalry attacks and rescues, and secret woodland fastnesses known only to the canniest frontiersman.
—Ian Frazier, The New Yorker, 15 July 2024
Recent Examples of Synonyms for fastness
Noun
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In a field experiment with hundreds of consultants, GPT-4 improved speed and quality on some knowledge tasks while performance dropped on other, seemingly similar tasks just outside its strengths.—
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Tapascott said speed alone no longer excites drivers.—
Noun
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McDonald said DeSantis also could be trying to shore up Republican strongholds to mitigate the losses generally experienced by the party in power during midterm elections.—
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Campbell’s main support always came from the union stronghold of Pueblo, in southern Colorado.—
Noun
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The strategy reflects McDonald's broader push to lean on nostalgia and popular partnerships to drive traffic and loyalty at a time when consumers are growing more cautious about spending, the outlet reported, citing a recent earnings call.—
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Guests are automatically enrolled in Intrepid Insiders, a loyalty program offering early access to sales and new itineraries.—
Noun
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Depending on the configuration and the mass-ratio, the spacecraft could go even faster, with some estimates placing its top velocity at 5% the speed of light.—
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This means that there is a way of stretching the velocity curve in one frame to match the steeper velocity curve in a later frame.—
Noun
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The fortress of intellectual property This is why the Warner bid is essential, Shapiro said, repeating one of his recent theories about the coming wave of disruption in media.—
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Walk in around the massive fortress with its cannons and tunnels.—
Noun
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Iwobi, nephew of former Nigeria international Jay-Jay Okocha, played for England at under-16 and under-17 levels before switching allegiance.—
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And that ever-reliable Republican allegiance is looking much less ironclad.—
Noun
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Catania’s Palazzo Biscari (a bastion of Rococo glory) occupies an entire block of the volcanic-stone city and is still occupied by descendants of the Biscari family.—
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Well, Orange County certainly had this reputation for so long as the conservative bastion, going back to not only the Klan days and then the John Birch Society after that.—
Noun
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Still, Mamdani thanked first responders for their dedication to saving lives in both blazes.—
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Know of a longtime volunteer in Rancho Bernardo who stands out above the rest for dedication, leadership and service?—
Cite this Entry
“Fastness.” Merriam-Webster.com Thesaurus, Merriam-Webster, https://www.merriam-webster.com/thesaurus/fastness. Accessed 12 Jan. 2026.
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