Rebound guy/girl is a guy/girl used on the sideline by an individual if he/she thinks his/her relationship is going to end.
“备胎”就是一个人留在身边备用以防上一段感情快要结束的暧昧男或暧昧女。
Rebound guy/girl would do anything for you or accompany you once you ask, for instance, having a lunch, seeing a film or going to a concert. Also, they would never go Dutch but take care of you for everything. Apart from that, they are likely to bring you gifts if they happen to be born loaded including luxury bags, laptops, jewelry as long as you are joyful.