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
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,
20 Jan. 2026
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
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
Yelena Moroz Alpert,
Architectural Digest,
20 Jan. 2026
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
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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The Beltline allows only Class 1 or 2 e-bikes and speeds of only up to 15 mph.
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Pfendler appears to have broken both the previous women's speed record as well as the men's speed record, according to records maintained by Ocean Rowing Society International, which adjudicates ocean-rowing achievements for Guinness World Records.
Noun
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History fans should look out for the climb up to the Château de Montségur, once a stronghold of the Cathar religious rebels, and scene of a bloody siege in 1244.
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According to the indictment made public this week, the Hoovers had strongholds over specific hotels and motels in their territory, including the Stadium Inn & Spas.
Noun
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When the Gold Cloaks march into the palace and proclaim their new loyalties, Rickard’s men defy him by laying down their swords, too.
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This column first addressed an employee’s duty of loyalty nine years ago, almost to the day.
Noun
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Your sentences have great velocity.
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The asteroid could, for example, be a contact binary, according to Michel, in which two separate bodies came together at low velocities.
Noun
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Was a wedding at that hulking fortress in Midtown Manhattan gauche?
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The footage opens with fortress-like coastal imagery before moving into large-scale period sets, suggesting the film will have the epic scope of Hugo’s story while grounding it in a raw visual language.
Noun
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Beginning on that day, Mercury invites everyone - creators, agencies, executives, and follow networks - to pledge their allegiance to Independent Podcasters Day via their website.
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Gabriel Zakuani, the former Peterborough United defender who made 29 appearances for DR Congo in the previous decade, played an important role in convincing Wan-Bissaka to switch international allegiance.
Noun
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Because Cook County and the city of Chicago remain a Democratic bastion, new voters will not have the choice of getting new ideas or a fresh set of eyes from an independent or a Republican candidate.
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These organizations claim to be bastions of journalism, Defenders of Democracy, and heroes in the fight for truth in government.
Noun
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Some attendees spent months creating their costumes, sewing patterns and 3D-printing props just to attend the convention, and that dedication was shared by many at Charlotte Big Anime.
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Even by these standards, some Costco fans’ dedication is next level.
Cite this Entry
“Fastness.” Merriam-Webster.com Thesaurus, Merriam-Webster, https://www.merriam-webster.com/thesaurus/fastness. Accessed 5 Jul. 2026.
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