The title of the novel is Exit West. This two words don’t have a specific meaning, you can interprete them in your own way. This sentence can indicate an emergency exit on a plane or in a building. This two words may also mean to move away from a specific place for any reason such as a war or a natural disaster. The title is composed by the word exit which mean to go out of a place or even a situation and west, which is a cardinal point so you can interprete this sentences with the meaning to go away from west or to go away from your country and move to west. The interpretation of this title can be very personal and soggettive so I think there can't be only a correct interpretation.