To dream of something being hollow represents situations or personality traits that lack substance. Something in your life that is empty, worthless, or insignificant.
Example: A man dreamed of standing on a hollow moon. In waking life he took a risk to face a fear and realized there was nothing to worry about. He fears were totally overblown.
Example 2: A woman dreamed of a hollow tree. In waking life she was beginning to feel that her job was empty and meaningless.