Usually the same as cold, or ice, namely that you may be holding back, freezing, your feelings about something. Or else you may have shut down on much of your sensitivity in life, perhaps to deal with loss, pain or disappointment. Such a huge block of ice may mean that an enormous amount of your energy and creativity is frozen along with your feelings.
The iceberg is often used in literature, and sometimes in dreams, as a symbol of consciousness. A little of your being you are aware of, like the ice above the surface. But the enormous bulk of self is invisible to view; beneath consciousness. See: Glacier