Zhao Gongming was quite adept at using metaphors. As he led Guo Feilong through layer upon layer of misty killing formations, he explained the concept of world will and the will of the Great Dao to him.
The world will is essentially the will of a world. A large cultivation world has the world will of a large cultivation world, while a small Heavenly Abode has the world will of a small Heavenly Abode.
The world will can also be understood as the Path of Heaven, also known as the power of the laws of the Path of Heaven, which are the rules and laws within a world.
The will of the Great Dao is a higher form of rules and laws.