[1] : The Collaborative International Dictionary of English v.0.48

unsound \unsound"\, a.
   not sound; not whole; not solid; defective; infirm; diseased.
   1913 webster -- unsound"ly, adv. -- unsound"ness, n.
   1913 webster
see also:
unsound"ly unsound"ness 

[2] : WordNet (r) 2.0

unsoundness
     n : a condition of damage or decay ant: soundness
see also:
soundness 

[3] : Bouvier's Law Dictionary, Revised 6th Ed (1856)

unsoundness. vide crib-biting; roaring; soundness. 

Unsoundness >> U Words
Unsoundness, definition of term: Unsoundness
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