unsound

adjective

1. 1

   of e.g. advice

2. 2

   physically unsound or diseased

   has a bad back

   a bad heart

3. 3

   suffering from severe mental illness

   of unsound mind

4. 4

   not sound financially

   unsound banking practices

5. 5

   not in good condition; damaged or decayed

   an unsound foundation

6. 6

   containing or based on a fallacy

   fallacious reasoning

   an unsound argument