A WIP (work in progress) limit is a strategy for preventing bottlenecks in software development.
Work in Progress limits are agreed upon by the development team before a project begins and are enforced by the team’s facilitator. For example, a team may divide the tasks that must be performed for a feature into design, code, test and deploy. When a WIP limit for a certain task has been reached, the team stops and works together to clear the bottleneck. The goal of working in this manner is meant to ensure that the entire team takes ownership of the project and produces high quality code.
I most online tools the WIP limit can be set by the team’s facilitator (e.g. ScrumMaster) to a fixed amount for a sprint. In JIRA this can be done in the Greenhopper plugin.