1. The period of time that begins with the decision to develop a software product and ends when the product is delivered. This cycle typically includes a requirements phase, design phase, implementation phase, test phase, and sometimes, installation and checkout phase. Contrast with software life cycle. 2. The period of time that begins with the decision to develop a software product and ends when the product is no longer being enhanced by the developer. 3. Sometimes used as a synonym for software life cycle.