The term 'non compos mentis' is a Latin phrase meaning 'not of sound mind'. This phrase is often used to describe someone who is mentally impaired or unable to think clearly. The crossword solutions for this term include ADDLED (6 letters), INSANE (6 letters), MAD (3 letters), BATTY (5 letters), LOONY (5 letters), DOTTY (5 letters), and IRRATIONAL (10 letters). All of these words are synonyms for the phrase 'non compos mentis' and can be used to describe someone who is not of sound mind.