A cross-functional team is a group of people with different functional expertise, working towards a common goal. It may include people from operations, engineering, quality and human resources departments. Generally, employees from all levels of an organization are included. Some members may come from outside the organization to add experience, expertise or a neutral unbiased view.
Cross-functional teams often function as self-directed teams assigned to a specific task which calls for the input and expertise of numerous departments.
Reference: Wikipedia - Cross-functional team.