verb hard·en \ ˈhär-dᵊn \
|Updated on: 11 Aug 2018

Definition of harden

hardened; hardening play \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 a : inure, toughen
  • harden troops
b : to inure to unfavorable environmental conditions (such as cold) often used with off
  • harden off seedlings before transplanting
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

Examples of harden in a Sentence

  1. The presence of certain substances in the blood can cause the arteries to harden.

  2. These additives are designed to harden the steel.

  3. substances that can harden the arteries

  4. The news has hardened opposition to the government.

  5. He had been hardened by his years of military service.

Recent Examples of harden from the Web

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'harden.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

First Known Use of harden

13th century

in the meaning defined at transitive sense 1

See Words from the same year
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biographical name Har·den \ ˈhär-dᵊn \

Definition of Harden

Sir Arthur 1865–1940 English chemist


biographical name

Definition of Harden

Maximilian 1861–1927 originally Felix Ernst Witkowski German writer

HARDEN Defined for English Language Learners


Definition of harden for English Language Learners

  • : to become hard or firm or to make (something) hard or firm

  • : to become more definite and strongly felt or to make (something) more definite and strongly felt

  • : to make (someone) hard : to make (someone) less emotional and less likely to feel sorry for other people

HARDEN Defined for Kids


verb hard·en \ ˈhär-dᵊn \

Definition of harden for Students

hardened; hardening
1 : to make or become hard or harder
  • By now the cement has hardened.
2 : to make or become hardy or strong Years of tough work had hardened his muscles.
3 : to make or become stubborn or unfeeling
  • She hardened her heart and refused to forgive him.

Seen and Heard

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resembling the blue of the sky

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