If you devour something in a dream, it can mean that you are trying to repress upsetting thoughts or emotions. You are keeping these thoughts and emotions inside of you where they cannot be revealed to others, or to yourself.
A dream about devouring something can represent destroying evil or taking in goodness.
Devouring something in a dream can mean that you are in need of spiritual or emotional nourishment. Your dreaming mind is interpreting your spiritual or emotional starvation as physical starvation. Devouring something in your dream is a way of alleviating your hunger.
A dream that you watch someone else devour something can be a sign that you are feeling neglected. Someone else is getting the comfort and satisfaction that you deserve. Watching someone else devour something can mean that you feel that someone else is getting the credit for your hard work.