Mentally unbalanced is a term used to describe someone who is suffering from a mental illness or disorder. It can refer to a wide range of conditions, from mild depression to severe psychosis. Two words that are often used to describe someone who is mentally unbalanced are 'MAD' and 'DAFT'. MAD is an informal term for someone who is mentally ill, while DAFT is a more lighthearted way of saying someone is foolish or silly.