adjective. noun. The definition of incumbent is laying on top of something. An example of incumbent is a cat lounging on its sleeping owner.Incumbent is defined as the person who is already in an elected office. An example of incumbent is the person who is currently the president.he definition of incumbent is laying on top of something. An example of incumbent is a cat lounging on its sleeping owner. Incumbent is defined as the person who is already in an elected office. An example of incumbent is the person who is currently the president.