un ‧ sound /ˌʌnˈsaʊnd◂/ BrE AmE adjective
1 . not based on facts or good reasons
ideologically/scientifically/ecologically etc unsound
a test that’s scientifically unsound
2 . an unsound building or structure is in bad condition:
The houses are structurally unsound.
3 . formal physically or mentally ill:
people of unsound mind (=people who are mentally ill)