unsound

adjective

un·​sound ˌən-ˈsau̇nd 

: not sound: such as

a

: not healthy or whole

an unsound horse

b

: not mentally normal : not wholly sane

of unsound mind

c

: not firmly made, placed, or fixed

structurally unsound

d

: not valid or true : invalid, specious

unsound beliefs

unsoundly

ˌən-ˈsau̇n(d)-lē 

adverb

Synonyms

• sick
• poorly
• bad
• ill
• unhealthy
• shaky

Examples of unsound in a Sentence

The roof is structurally unsound.

disgruntled relatives tried to prove that the woman was of unsound mind when she made her will

Recent Examples on the Web

The approach that the Great Barrington Declaration laid out was, at the time, widely denounced by public-health experts, including the World Health Organization and then–NIH director Francis Collins, as dangerous and scientifically unsound. —Katherine J. Wu, The Atlantic, 9 June 2025

At the heart of this problem lies the influence of vocal anti-vaccine rhetoric that is not only scientifically unsound but also profoundly irresponsible. —Amar Duggirala, Baltimore Sun, 23 Apr. 2025

Black Mirror returns for a seventh season, with a star lineup that includes Rashida Jones, Tracee Ellis Ross, and Issa Rae—who enter the bizarre realms of the sci-fi series with unsound comedy and deep human emotion. —Malik Peay, Essence, 17 Apr. 2025

The money would go to Metro, the physically unsafe and fiscally unsound public transit system that saw its ridership peak in the 1980s. —Susan Shelley, Oc Register, 12 Apr. 2025

Word History

First Known Use

14th century, in the meaning defined above

Phrases Containing unsound

• of unsound mind

Rhymes for unsound

• abound
• aground
• around
• astound
• background
• campground
• clothbound
• confound
• earthbound
• eastbound
• expound
• fairground

Kids Definition

unsound

adjective

un·​sound ˌən-ˈsau̇nd 

ˈən-

1

: not healthy or whole

an unsound horse

2

: not mentally normal : not wholly sane

of unsound mind

3

: not firmly made, placed, or fixed

an unsound structure

4

: not based on truth or logic

unsound arguments

unsoundly

-ˈsau̇n-(d)lē 

adverb

unsoundness

-ˈsau̇n(d)-nəs

noun

Medical Definition

unsound

adjective

un·​sound -ˈsau̇nd 

: not sound: as

a

: not healthy or whole

an unsound limb

an unsound horse

b

: not mentally normal : not wholly sane

of unsound mind

c

: not fit to be eaten

unsound food

unsoundness noun

Legal Definition

unsound

adjective

un·​sound ˌən-ˈsau̇nd 

: not sound: as

a

: not healthy or whole

b

: not mentally normal : not wholly sane

of unsound mind

c

: not firmly made, placed, or fixed

d

: not valid or true

an unsound argument

unsoundly adverb

unsoundness noun