When describing something that's large or substantial in size, there are plenty of synonyms that can be used instead of the phrase "is big." Depending on the context, you can opt for words like massive, enormous, spacious, extensive, bulky, colossal, and hefty. If you're looking to describe something that's impressive, grand, or stately, consider using synonyms such as majestic, monumental, impressive, or grandiose. On the other hand, if you want to describe something that's overly large or excessive, you might use words like bloated, inflated, or exaggerated. In any case, using a variety of synonyms can help keep your writing fresh and varied, while giving your readers a richer understanding of the subject at hand.