The phrase "going belly up" is an informal term that refers to a situation or a business enterprise failing completely. Antonyms for this phrase include thriving, succeeding, flourishing, prospering, and growing. If a company is thriving, it means it is growing, expanding, and doing well financially. Companies that are succeeding are profitable, stable, and competitive. Flourishing businesses have vibrant operations and are attracting new clients. Prosperous companies have ample resources and can take on new ventures. These antonyms demonstrate that going belly up is not the only possible outcome for a business or undertaking, and that there are many ways for success to be achieved.