# harden

/ˈhɑɹdən/ (US) · /hˈɑːdən/ (UK)

Source: https://englishreference.com/word/harden
Updated: 2026-08-15

## Senses

### 1. to become solid

verb · CEFR B1

to become firm, stiff, or solid.

For teachers: to transition from a liquid, soft, or malleable state to a solid or rigid one.

- Wait for the concrete to harden before you try to walk on it.
- The molten lava began to harden as soon as it came into contact with the cool ocean water.

Usage: Often used as an intransitive verb describing natural processes.

### 2. to make something solid

verb · CEFR B1

to make something firm or solid.

For teachers: to cause a substance to become rigid or resistant to pressure.

- The cold weather will harden the ground, making it difficult to dig.
- Special chemicals are added to the mixture to harden the plastic during the manufacturing process.

Usage: Used transitively when an external force or agent causes the change.

### 3. to become less sensitive

verb · CEFR B2

to become more tough or less easily upset by difficult things.

For teachers: to become emotionally callous, resilient, or less susceptible to sympathy or pain.

- Years of working in the emergency room had hardened his heart to suffering.
- The soldiers had been hardened by months of combat, showing little emotion even in dire circumstances.

Usage: Frequently used with 'heart' or 'attitude' as the object.

### 4. to secure a computer system

verb · CEFR C1 · Technical

to make a computer system or website safer against hackers.

For teachers: to reduce a system's vulnerability by reducing its attack surface and layering technical protections.

- The IT team needs to harden the server before we launch the new site.
- System administrators must harden the operating system by disabling unnecessary services and enforcing strict password policies.

Usage: A transitive verb used specifically in the context of cybersecurity.

## Examples

- The wet cement will harden in a few hours.
- The government's stance began to harden as the negotiations reached their third week without a resolution.
- As the molten lava cools and begins to harden into basalt, it creates the jagged landscapes characteristic of volcanic islands.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.