The term 'highly influential' can be summarized by the word 'seminal, ' which means having a lasting and significant impact. It is often used to describe people, ideas, or works that have had a major influence on a particular field or area of study. For example, a seminal work in the field of psychology might be Sigmund Freud's The Interpretation of Dreams. Similarly, a highly influential person might be someone like Mahatma Gandhi, who was instrumental in leading India to independence.