Mentally sound is a term used to describe someone who is mentally healthy and stable. The crossword solutions for this term are SANE (4 letters), NORMAL (6 letters), LUCID (5 letters), and ONONESROCKER (12 letters). SANE is an acronym for 'SANE in all respects' and is used to describe someone who is rational and has a sound mind. NORMAL is used to describe someone who is not exhibiting any abnormal behavior or mental illness. LUCID is used to describe someone who is clear-minded and able to think logically. Finally, ONONESROCKER is a phrase used to describe someone who is mentally stable and not easily swayed by external influences.