adj., -er, -est.

1. Not dependably strong or solid.
2. Not physically or mentally healthy.
3. Not true or logically valid; fallacious: an unsound conclusion.

unsoundly un·sound'ly adv.
unsoundness un·sound'ness n.

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adjective

1. Not physically strong: decrepit, delicate, feeble, flimsy, fragile, frail, infirm, insubstantial, puny, unsubstantial, weak, weakly. See strong/weak.
2. Afflicted with or exhibiting irrationality and mental unsoundness: brainsick, crazy, daft, demented, disordered, distraught, dotty, insane, lunatic, mad, maniac, maniacal, mentally ill, moonstruck, off, touched, unbalanced, wrong. Informal bonkers, cracked, daffy, gaga, loony. Slang bananas, batty, buggy, cuckoo, fruity, loco, nuts, nutty, screwy, wacky. Chiefly British crackers. Law non compos mentis. Idioms: around the bend, crazy as a loon, mad as a hatter, not all there, nutty as a fruitcake, offout ofone's head, off one's rocker, of unsound mind, out of one's mind, sick in the head, stark raving mad. See sane/insane.
3. Containing fundamental errors in reasoning: fallacious, false, illogical, invalid, sophistic, specious, spurious. See correct/incorrect, true/false.
4. Containing an error or errors: erroneous, fallacious, false, inaccurate, incorrect, mistaken, off, untrue, wrong. Idioms: all wet, in error, off base, offwide ofthe mark. See correct/incorrect.
5. Not wise: ill-advised, ill-considered, impolitic, imprudent, indiscreet, injudicious, unwise. See wise/foolish.

adj

Definition: not well; flimsy
Antonyms: safe, sound, stable, strong, well

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Descriptive of a plaster, slaked lime, cement, or other mortar which contains particles that may expand.

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Said of an animal, usually a horse, which has been examined for soundness and found to be unsatisfactory.

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Dansk (Danish)
adj. - usund, syg, sygelig, dårlig, ustabil, upålidelig

idioms:

• of unsound mind    sindsforvirret

Nederlands (Dutch)
niet degelijk, zwak, ziek (elijk), ongegrond, onorthodox (ketters), onbetrouwbaar, vals

Français (French)
adj. - en mauvais état, peu valable (un argument), (Fin) douteux

idioms:

• of unsound mind    (Jur) ne pas jouir de toutes ses facultés mentales

Deutsch (German)
adj. - krank, morsch, unzuverlässig, unvertretbar, anfechtbar

idioms:

• of unsound mind    unzurechnungsfähig

Ελληνική (Greek)
adj. - σαθρός, σφαλερός, επισφαλής, ασθενής, μη υγιής

idioms:

• of unsound mind    (νομ.) μη έχων σώας τας φρένας

Italiano (Italian)
malsano, guasto, erroneo

idioms:

• of unsound mind    incapace di mente

Português (Portuguese)
adj. - doente, infundado, não sólido

idioms:

• of unsound mind    com a mente perturbada

Русский (Russian)
нездоровый, испорченный, гнилой, дефектный, ненадежный, необоснованный (аргумент и пр.), неглубокий (сон)

idioms:

• of unsound mind    душевнобольной

Español (Spanish)
adj. - enfermizo

idioms:

• of unsound mind    demente, fuera de juicio

Svenska (Swedish)
adj. - inte frisk, sjuk, sjuklig, ankommen, angripen, anfrätt, osund, osäker, riskabel

中文（简体） (Chinese (Simplified))
不健全的, 不稳固的, 谬误的

idioms:

• of unsound mind    精神失常的因而不须对自己的行为负责的

中文（繁體） (Chinese (Traditional))
adj. - 不健全的, 不穩固的, 謬誤的

idioms:

• of unsound mind    精神失常的因而不須對自己的行為負責的

한국어 (Korean)
adj. - 건전하지 못한, 불합리한, 신용이 안가는

日本語 (Japanese)
adj. - 健康でない, 不安定な, 根拠に乏しい, 不合理な, 健全でない, 浅い, 信用できない

idioms:

• of unsound mind    精神異常の

العربيه (Arabic)
‏(صفه) لا اساس, له, كاذب, كافر, غير موثوق به, معيوب‏

עברית (Hebrew)
adj. - ‮לא בקו-הבריאות, רקוב, רעוע, חסר-יסוד, כוזב, לא-מהימן, כופר, לא-עמוקה (שינה), מרושע‬

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