The term 'Occupy Completely' is a crossword solution that can be filled in with the word 'FILL', which is a four-letter word. The term 'Occupy Completely' is used to describe a situation in which something is completely taken up or filled with something else. This could refer to a physical space, such as a room, or it could refer to a mental space, such as a person's thoughts or emotions. In either case, the term implies that the space is completely taken up or filled with something else.