There are plenty of synonyms for the phrase "is gathering." Some examples of these include accumulating, amassing, collecting, congregating, convening, grouping, huddling, meeting, assembling, and clustering. Depending on the context in which the phrase is being used, different synonyms may be more appropriate or carry slightly different connotations. For example, "congregating" and "meeting" imply more intentional and organized gatherings, while "huddling" suggests a more casual or impromptu gathering. Regardless of the specific synonym chosen, they all communicate a sense of people, things, or ideas coming together in one place or in one way.