It is the profound research of a particular term and cannot be defined in one sentence.This kind of essay requires the students to pick a term that cannot be similarly described by several persons.
Also it may be called an extended definition essay.
A definition essay explores the history of a certain term and the author’s personal understanding of the particular concept or term.
Also the essay should consider what experiences and research the author has developed.
Then proceed to more specific dictionaries related to certain disciplines (like music, medicine, physics, philosophy, etc.).
Check reference books to find quotations or definitions made by famous people.