How would you define Natural Order in relation to Macbeth?
So true. The Elizabetheans saw, or assigned, order to all aspects of life. From the Divine Rite of Kings to the role of the Church, order gave purpose and predictability to a difficult and confusing existence.
Macbeth and his wife usurp this system by pursuing things out of order. The prophesy of the sisters provoked them to take action to attain an "effect" before the cause could naturally occur. By inverting cause and effect, Macbeth and his sweet wife lose their sense and their sanity.
Refer to the Matrix (I can't believe I am referring to this movie). The Oracle tells Neo that it is ok that he will break a vase. In turning to see which vase he might break, he breaks a vase. The natural order is tampered with and it leaves an uneasy feeling.
The Elizabethan order of the universe places God at the top, followed by the sovereign (kings/queens/royalty), noblemen, clergy, landowners...and so on, right down to plants and rocks. When the order is upset, such as when Macbeth murders a king, things go badly for everyone until right order is restored. There are many sources on the Internet where you can read about the Elizabethan world view or order of the universe.