Forming ranks is a phrase that indicates the organization of people or things in a particular order or manner. There are various synonyms that can be used interchangeably with the term form ranks. One such synonym could be "fall in," which means to align oneself in an orderly manner. Another synonym could be "assemble," which denotes the gathering of individuals in a particular location or formation. "Line up" is another alternative term that suggests putting people or objects in a straight row or queue. "Arrange" and "marshal" can also be used as synonyms for form ranks, indicating the process of organizing and putting things in order.