Immensity is a word that describes something that is vast, enormous or immense. Some synonyms for immensity include hugeness, enormity, grandeur, magnitude, vastness, expansiveness, expanse, greatness, size, and largeness. These words are all interchangeable and can be used to describe anything that is large in size or scale. For example, you could say that the immensity of the ocean is awe-inspiring, or that the immensity of the mountain range was breathtaking. Ultimately, these words can help you to vividly describe things in a way that captures their size or scale, and helps to convey their grandeur.