The term 'Complete Group' can be defined as a SET of three letters. This term is often used in crossword puzzles, where the goal is to fill in the blanks with words that fit the clues given. The letters in the SET are usually related to each other in some way, such as being part of a phrase or having a common theme. The SET can also be used to represent a group of people or objects that are all related in some way. For example, a complete group could be a family, a team, or a group of friends.