"Firming up" refers to strengthening or solidifying something, usually to achieve a more stable or structured state. There are a variety of synonyms that can be used interchangeably depending on the context. Some possible options include consolidating, reinforcing, tightening, securing, fortifying, and stiffening. These words may be used in a wide range of scenarios, from physical fitness to financial planning to organizational management. Whether you're working on improving your physique, making strategic decisions for your business, or trying to create a more cohesive team, firming up can be an important step towards achieving your goals. With the right vocabulary at your disposal, you can communicate your intentions clearly and effectively.