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
Synonyms & Similar Words
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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
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.—
Arkansas Online,
Arkansas Online,
8 Jan. 2026
-
Tapascott said speed alone no longer excites drivers.—
Aamir Khollam,
Interesting Engineering,
8 Jan. 2026
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.—
Mike Schneider,
Los Angeles Times,
8 Jan. 2026
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Campbell’s main support always came from the union stronghold of Pueblo, in southern Colorado.—
Dave Marston,
Denver Post,
6 Jan. 2026
Noun
-
And if that can happen to retail giants with decades of consumer goodwill, imagine the stakes for entertainment and cultural brands — where loyalty is fleeting, audiences are global and competition is relentless.—
Kimberly S. Reed,
Rolling Stone,
7 Nov. 2025
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Themes of love, loyalty and trust could also be tested under the weight of change.—
Valerie Mesa,
PEOPLE,
7 Nov. 2025
Noun
-
His velocity was up a bit in the second half, and his strikeout rate also jumped from 31% to 39%, so there's a case to be made that bad luck amplifies a slight regression from arguably the best reliever in the game to merely one of the best 10 to 15 in the league.—
Aaliyan Mohammed,
MSNBC Newsweek,
8 Nov. 2025
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In the modern landscape of personalized diagnostics, drug research, development, and manufacturing, data integrity and velocity of the product-to-market are everything.—
Daniel Fusch,
USA Today,
6 Nov. 2025
Noun
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Colina Pousada Spa Perched high on a hilltop, Colina Pousada Spa offers 180-degree views, from the island’s tallest peak to the old fortress.—
Carla Vianna,
Travel + Leisure,
5 Nov. 2025
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Such structures, including residences and fortresses, were created by religious authorities and noble families, according to the city’s tourism website.—
Sam Gillette,
PEOPLE,
3 Nov. 2025
Noun
-
The glittering gastro gem shines brightly with resourceful chefs embracing a diverse array of culinary traditions, often eschewing allegiance to strictly Southern cooking.—
Nevin Martell,
USA Today,
7 Nov. 2025
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After all the tariffs, boycotts, and bruised egos, both countries have been left to reckon with lasting economic scars and shifting allegiances.—
Dave Gordon,
The Washington Examiner,
7 Nov. 2025
Noun
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The new district is a throwback of sorts to Orange County’s mid- to late-20th-century role as a bastion of conservative Republicanism.—
David Mark,
The Washington Examiner,
7 Nov. 2025
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His critics on the left say these ideas are unrealistic — even in a liberal bastion like New York City.—
Elena Moore,
NPR,
2 Nov. 2025
Noun
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Still, Mamdani thanked first responders for their dedication to saving lives in both blazes.—
Angel Saunders,
PEOPLE,
7 Jan. 2026
-
Know of a longtime volunteer in Rancho Bernardo who stands out above the rest for dedication, leadership and service?—
Elizabeth Marie Himchak,
San Diego Union-Tribune,
6 Jan. 2026
Cite this Entry
“Fastness.” Merriam-Webster.com Thesaurus, Merriam-Webster, https://www.merriam-webster.com/thesaurus/fastness. Accessed 9 Jan. 2026.
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