1 happening one after the other 一个接一个地；连续地: They played two games back to back. 他们连续打了两场比赛。

2 (used about two people) sitting or standing next to each other, usually with their backs touching ﹙二人﹚背靠背地: The girls stood back to back to see who was taller. 这两个女孩背靠背站着，看谁身材高。