The term 'highly vigilant' can be summarized as being ALERT and watchful. It is often used to describe someone who is constantly on the lookout for potential danger or problems. This could be a security guard, a police officer, or even a parent watching over their children. Being highly vigilant requires one to be aware of their surroundings and to be prepared to take action if necessary. The crossword solution for this term is 'ALERT, ' which is an appropriate description of someone who is highly vigilant.