A use case is a description of a focused interaction where the user achieves a goal. For example, in a banking app it might be to pay a bill. A use case can be thought of as a very short scenario. Use cases are a critical part of agile software development processes. In these the system is built incrementally use-case by use-case, with each use case implemented in a single sprint. In some ways this sounds similar to the iterative design cycle, but it can pose difficulties for UX design especially for more global properties such as consistency.
Used in glossary entries: consistency, iterative design, scenario, user experience design