as in to freeze
to become physically firm or solid
wait for the modeling clay to firm up before handling the finished pot
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Recent Examples of Synonyms for firm (up)
Verb
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An ancient microorganism that figured out how to keep its cellular structures intact through 40,000 years of deep freeze could someday inspire a product that keeps a soldier’s skin from freezing on an Arctic patrol.—
Ryan Brennan,
Miami Herald,
13 Feb. 2026 -
How long temperatures fall below freezing matters.—
Newsroom Meteorologist,
Houston Chronicle,
13 Feb. 2026
Verb
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For years, this unspoken truth has hardened her, shaping her into a woman of precision and emotional distance — a mother who learned survival through silence.—
Melanie Goodfellow,
Deadline,
5 Feb. 2026
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Water your plants regularly during the hardening off process, but slowly decrease how much water your plants receive.—
Lauren Landers,
Better Homes & Gardens,
5 Feb. 2026
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“Firm (up).” Merriam-Webster.com Thesaurus, Merriam-Webster, https://www.merriam-webster.com/thesaurus/firm%20%28up%29. Accessed 15 Feb. 2026.
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