The word "grave" can be used in different contexts, and there are a variety of synonyms that could be used to describe it. When referring to a burial site or place, "cemetery," "mausoleum," or "tomb" can be used. For situations that are serious or solemn, "solemn," "serious," "weighty," or "momentous" could be appropriate. Additionally, for situations that are grim or dangerous, "dire," "grim," "serious," or "threatening" could be used. For describing someone as serious or stern, "stern," "grave," or "serious-minded" could be applicable. Depending on the context and tone, there are a range of synonyms that can be used in place of "grave".