The crossword solution for the term 'Frighten to the Core' is 'UNMAN, ' which is a five-letter word. UNMAN means to reduce someone to a state of extreme fear or terror, often to the point of being paralyzed with fear. It can also mean to make someone feel powerless or helpless. This term is often used in horror movies and other forms of media to describe a character's reaction to a particularly frightening situation.