un·​sound | \ˌən-ˈsau̇nd \

Definition of unsound 

: 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

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Other Words from unsound

unsoundly \ˌən-​ˈsau̇n(d)-​lē \ adverb

Synonyms & Antonyms for unsound


balmy, barmy [chiefly British], bats, batty, bedlam, bonkers, brainsick, bughouse [slang], certifiable, crackbrained, cracked, crackers, crackpot, cranky [dialect], crazed, crazy, cuckoo, daffy, daft, demented, deranged, fruity [slang], gaga, haywire, insane, kooky (also kookie), loco [slang], loony (also looney), loony tunes (or looney tunes), lunatic, mad, maniacal (also maniac), mental, meshuga (or meshugge), moonstruck, non compos mentis, nuts, nutty, psycho, psychotic, scatty [chiefly British], screwy, unbalanced, unhinged, wacko (also whacko), wacky (also whacky), wud [chiefly Scottish]


balanced, compos mentis, sane, sound, uncrazy

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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

Lumber companies can sell some of the wood to recoup their expenses, but many of the trees are too decayed or structurally unsound to sell. Umair Irfan, Vox, "California has 129 million dead trees. That’s a huge wildfire risk.," 1 Sep. 2018 There's no hype for this adaptation of a schlocky 1997 novel about a scientifically unsound super-shark. Sam Machkovech, Ars Technica, "The Meg film review: We’re going to need a stupider boat," 10 Aug. 2018 Take it from one unsound sleeper: A little misting can go a long way. Brooke Bobb, Vogue, "5 Body Mists That Promise a Better Night’s Sleep—And Glowing Skin in the Morning," 29 July 2018 But the larger part for Democrats in Georgia is that their hope for revival is predicated on an unsound theory: That the level of Republican support among a shrinking percentage of white voters was relatively static. Chris Stirewalt, Fox News, "Georgia's disappointing Democrats," 22 May 2018 As a legal question, experts say Trump’s proposition is unsound. Salvador Rizzo, Washington Post, "President Trump’s misconceptions about immigration courts and law," 26 June 2018 The New York Department of Financial Services found that from 2007 to 2013, Deutsche Bank engaged in improper, unsafe, and unsound conduct in its currency trading business. BostonGlobe.com, "SHYFT Analytics to be acquird by New York company," 21 June 2018 The New York Times, the White House, America—are in fact built upon the softest of foundations: humans, messy and complicated and structurally unsound. Megan Garber, The Atlantic, "The Fourth Estate in the Age of Bad Faith," 15 June 2018 Nowhere have the challenges been steeper than Big Thompson Canyon, where floodwaters scoured away not only pavements and guardrails but roadbeds and subsurface geology, effectively leaving sections of highway unsound and unsafe. Daniel Cusick, Scientific American, "Colorado Charts a New Path Away from Floodwaters," 25 May 2018

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

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First Known Use of unsound

14th century, in the meaning defined above

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Statistics for unsound

Last Updated

4 Dec 2018

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Time Traveler for unsound

The first known use of unsound was in the 14th century

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More Definitions for unsound



English Language Learners Definition of unsound

: not based on truth or logic : not showing good judgment

: poorly built or in bad condition


un·​sound | \ˌən-ˈsau̇nd \

Kids Definition of unsound

1 : not based on good reasoning or truth an unsound argument unsound advice

2 : not firmly made or placed an unsound building

3 : not healthy or in good condition unsound teeth

4 : being or having a mind that is not normal


un·​sound | \-ˈsau̇nd \

Medical Definition of unsound 

: 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

Other Words from unsound

unsoundness noun

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un·​sound | \ˌən-ˈsau̇nd \

Legal Definition of unsound 

: 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

Other Words from unsound

unsoundly adverb
unsoundness noun

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More from Merriam-Webster on unsound

Rhyming Dictionary: Words that rhyme with unsound

Thesaurus: All synonyms and antonyms for unsound

Spanish Central: Translation of unsound

Nglish: Translation of unsound for Spanish Speakers

Britannica English: Translation of unsound for Arabic Speakers

Comments on unsound

What made you want to look up unsound? Please tell us where you read or heard it (including the quote, if possible).


a nest or breeding place

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