Definition of harden
- hardened his heart
- harden off seedlings before transplanting
- her face hardened at the thought
- plants hardened off before the first frost
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.
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.
: 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
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