The Collaborative International Dictionary of English v.0.48:

Sound \Sound\, a. [Compar. Sounder; superl. Soundest.] [OE.
   sound, AS. sund; akin to D. gezond, G. gesund, OHG. gisunt,
   Dan. & Sw. sund, and perhaps to L. sanus. Cf. Sane.]
   1. Whole; unbroken; unharmed; free from flaw, defect, or
      decay; perfect of the kind; as, sound timber; sound fruit;
      a sound tooth; a sound ship.
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   2. Healthy; not diseased; not being in a morbid state; --
      said of body or mind; as, a sound body; a sound
      constitution; a sound understanding.
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   3. Firm; strong; safe.
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            The brasswork here, how rich it is in beams,
            And how, besides, it makes the whole house sound.
                                                  --Chapman.
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   4. Free from error; correct; right; honest; true; faithful;
      orthodox; -- said of persons; as, a sound lawyer; a sound
      thinker.
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            Do not I know you a favorer
            Of this new seat? Ye are nor sound.   --Shak.
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   5. Founded in truth or right; supported by justice; not to be
      overthrown on refuted; not fallacious; as, sound argument
      or reasoning; a sound objection; sound doctrine; sound
      principles.
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            Hold fast the form of sound words, which thou hast
            heard of me.                          --2 Tim. i.
                                                  13.
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   6. heavy; laid on with force; as, a sound beating.
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   7. Undisturbed; deep; profound; as, sound sleep.
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   8. Founded in law; legal; valid; not defective; as, a sound
      title to land.
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   Note: Sound is sometimes used in the formation of
         self-explaining compounds; as, sound-headed,
         sound-hearted, sound-timbered, etc.
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   Sound currency (Com.), a currency whose actual value is the
      same as its nominal value; a currency which does not
      deteriorate or depreciate or fluctuate in comparision with
      the standard of values.
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