unsound

adjective4

1. •
   Not whole, not solid, defective.

   • In the ensuing financial panic, many persons sustained heavy losses, and large numbers of unsound schemes succumbed. — 1946
2. •
   Not good, unreliable.

   • You would not like Nietzsche, sir. He is fundamentally unsound. — 1919
3. •
   Not sound
4. •
   Infirm, diseased.

   • ... A horse labouring under a temporary injury, capable of being speedily cured, is not unsound within the meaning of a warranty of soundness ... — 1822