It is when a man will not speak to you about anything difficult or out of his comfort zone without having a think, he just hides in the "cave" in his head until he is ready to come to his own conclusion. It is all about waiting for them to emerge if you want show you are understanding and supporting them.
When faced with any large decision or emotional stuff, men need to think matters through in their own head we call this "dansinthecaveagain". To get their thoughts straight before others influence interjects or undue complications are added. Once finished in the cave men will return to rethink any other changes that may occur. This is a long process which can be utterly frustrating to witness, stay the course girls they always come out for food/fun/football fixtures eventually.