1. a discussion held at the end of a task in order to conduct a review and clear up any remaining issues
the boss called us in for a wash-up after the project was completed
A 'wash-up' or a 'wash-up meeting' takes place at the end of a project to review its success (or not) and ensure that everything has been covered. A wash-up meeting is used to evaluate the success of a project and to identify learning outcomes or to review the process. This is very much a business term, so you are unlikely to hear it used in a social context.