The phrase "to line up" means to arrange or organize in a straight row, either physically or figuratively. It can be used both as a transitive verb and an idiomatic expression. When referring to physical arrangement, it implies that objects or people are placed side by side in a single file order. In the context of sports teams, "to line up" means for players to take their positions on the field before the game starts. Figuratively, "to line up" can mean to align with something else, such as opinions, goals, or plans. For example, if someone says they are going to "line up" behind a particular candidate in an election, it means that they support and agree with their views and policies.