WordWeb Online

1. Containing or based on a fallacy
   "an unsound argument";
   - fallacious
    
2. Suffering from severe mental illness
   "of unsound mind";
   - mentally ill, unstable
    
3. Physically unsound or diseased
   "an unsound limb"; "unsound teeth";
   - bad, unfit
    
4. Of e.g. advice
    
5. Not in good condition; damaged or decayed
   "an unsound foundation"
    
6. Not sound financially
   "unsound banking practices"

Derived forms: unsounder, unsoundest

See also: bad, broken, corroded, damaged, decayed, flakey [informal], flaky [informal], high-risk, injured, insane, invalid, long, risky, rotted, rotten, speculative, undependable, unfit, unhealthy, unreliable, unwholesome, wildcat

Antonym: sound

Encyclopedia: Unsound