infirm

American  

[in-furm] / ɪnˈfɜrm /

adjective

1. feeble or weak in body or health, especially because of age; ailing.

   Synonyms:

   weak

   Antonyms:

   strong

2. unsteadfast, faltering, or irresolute, as persons or the mind; vacillating.

   infirm of purpose.

   Synonyms:

   indecisive

   Antonyms:

   strong

3. not firm, solid, or strong.

   an infirm support.

   Synonyms:

   unsteady, shaky, tottering, rickety, weak

   Antonyms:

   strong

4. unsound or invalid, as an argument or a property title.

   Synonyms:

   weak

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verb (used with object)

1. to invalidate.

infirm British  

/ ɪnˈfɜːm /

adjective

1. 1. weak in health or body, esp from old age

   2. ( as collective noun; preceded by the )

      the infirm

2. lacking moral certainty; indecisive or irresolute

3. not stable, sound, or secure

   an infirm structure

   an infirm claim

4. law (of a law, custom, etc) lacking legal force; invalid

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Other Word Forms

• infirmly adverb
• infirmness noun

Etymology

Origin of infirm

1325–75; Middle English infirme < Latin infirmus. See in- ³, firm ¹

Explanation

To be infirm is to be physically weak. If your great grandmother can't get around without a walker or a wheelchair, you might describe her as infirm. The adjective infirm is most often used to talk about elderly people whose bodies don't work as well as they used to — there's an implication of old age in the word. You could also describe an infirm person as decrepit or feeble. Sometimes a person's morals or character are described as infirm, which means you can't count on them to do the right thing. The Latin root, infirmus means "weak or feeble," or alternately, "superstitious or inconstant."

Example Sentences

In early scenes, he has a small curved line denoting a chubby chin, which changes over time to straight lines on each cheek, narrowing his face when he is old and infirm.

From MarketWatch • Mar. 16, 2026

The MoD has previously vowed to speed up the awards process after it was criticised for handling applications too slowly, particularly for elderly and infirm veterans.

From BBC • Feb. 18, 2026

Humanoid robots could assist the elderly or infirm.

From The Wall Street Journal • Oct. 8, 2025

Staples literally got the sick and infirm to stand up.

From Salon • Jun. 17, 2025

Jon had sent ten of the Mole’s Town wildlings to each of them: green boys, old men, some wounded and infirm, but all capable of doing work of one sort or another.

From "A Dance with Dragons" by George R. R. Martin

Related Words

• ailing
• anemic
• decrepit
• feeble
• frail
• ill
• insecure
• unstable