hardened; hardening
ˈhärd-niŋ 
ˈhär-dᵊn-iŋ
1
: to make hard or harder
2
: to confirm in disposition, feelings, or action
especially
: to make callous
hardened his heart
3
4
: to protect from blast, heat, or radiation (as by a thick barrier or placement underground)
1
: to become hard or harder
2
a
: to become firm, stable, or settled
b
: to assume an appearance of harshness or severity
her face hardened at the thought
3
: to become gradually acclimatized to unfavorable conditions
—often used with off
plants hardened off before the first frost
Synonyms
Examples of harden in a Sentence
The presence of certain substances in the blood can cause the arteries to harden.
These additives are designed to harden the steel.
substances that can harden the arteries
The news has hardened opposition to the government.
He had been hardened by his years of military service.
Recent Examples on the Web
Remember to harden off the seedlings for a week or two before transplanting to avoid transplant shock.
10.
—
Lauren Landers, Better Homes & Gardens, 4 Feb. 2025
Trump is adding to the pressure with mass deportations—then hoping to contain whatever erupts by simply hardening the southern border.
—Will Freeman, The Atlantic, 29 Jan. 2025
What Causes Gallstones? Gallstones form when substances like cholesterol and bile salts harden into solid particles inside the gallbladder.
—Jonathan Granoff, Newsweek, 29 Jan. 2025
At the Oakland news conference Wednesday, local politicians and nonprofit leaders gathered to denounce the Trump Administration’s threats of mass deportations and make plans to harden state laws.
—Sierra Lopez, The Mercury News, 23 Jan. 2025
See all Example Sentences for harden 
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.
Lauren Landers, Better Homes & Gardens, 4 Feb. 2025
Trump is adding to the pressure with mass deportations—then hoping to contain whatever erupts by simply hardening the southern border.
—Will Freeman, The Atlantic, 29 Jan. 2025
What Causes Gallstones? Gallstones form when substances like cholesterol and bile salts harden into solid particles inside the gallbladder.
—Jonathan Granoff, Newsweek, 29 Jan. 2025
At the Oakland news conference Wednesday, local politicians and nonprofit leaders gathered to denounce the Trump Administration’s threats of mass deportations and make plans to harden state laws.
—Sierra Lopez, The Mercury News, 23 Jan. 2025
See all Example Sentences for harden
Dictionary Entries Near harden
Cite this Entry
“Harden.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/harden. Accessed 10 Feb. 2025.
Copy CitationKids Definition
harden
verb
hard·en
ˈhärd-ᵊn
hardened; hardening
ˈhärd-niŋ
-ᵊn-iŋ
1
: to make or become hard or harder
2
: to make unfeeling or unsympathetic
hardened his heart
3
: to make or become hardy or strong
muscles hardened by exercise
4
: to protect from blast, heat, or radiation (as by a thick barrier or by placing underground)
hardened missile sites
5
a
: to become firm, stable, or settled
b
: to express harshness
hardener
noun
ˈhärd-nər
-ᵊn-ər
Biographical Definition
Harden
2 of 2biographical name (2)
Maximilian 1861–1927 originally Felix Ernst Witkowski German writer
Love words? Need even more definitions?
Merriam-Webster unabridged
Share