The definition of ready in Agile is the criteria that must be met in order for a user story to be considered ready for development. The definition of ready helps to ensure that the development team has a clear understanding of what is expected of the user story and that all necessary information and resources are available before development begins. The definition of ready is an important part of the Agile development process, as it helps to ensure that the development team is able to make steady progress towards their sprint goal.