A roadblock is an obstacle or barrier that prevents someone from achieving their goal. It can refer to a physical blockage on a road, such as debris or fallen trees, which makes it difficult for vehicles to pass. Figuratively, a roadblock can also mean any obstruction or hindrance that stands in the way of progress or success. For example, if someone is trying to complete a project but keeps running into problems and setbacks, they might say there's a "roadblock" preventing them from moving forward.