One common synonym for the term "big person" is "adult," which refers to a person who has reached the age of maturity and is no longer considered a child. Another synonym for "big person" is "grown-up," which implies that a person has matured both physically and emotionally. The term "elder" can also be used to refer to a big person, particularly someone who is older and holds a position of authority or respect in a particular community. Finally, the word "mature" can also be used as a synonym for "big person," as it implies a level of emotional and intellectual development that comes with age and experience.