The term 'unsociable sort' can be defined as a LONER, which is a person who prefers to be alone and avoids social interaction. This term can also refer to someone who is shy or introverted. The crossword solution for this term is 'LONER, ' which is a five-letter word. A LONER is someone who prefers to be alone and does not enjoy socializing with others. They may feel uncomfortable in large groups or in unfamiliar situations. Loneliness can be a symptom of depression or other mental health issues, so it is important to seek help if needed.