One-upper is an annoying person who responds to hearing someone else’s experience or problem by immediately telling a similar story about themselves with a much more fantastic (or terrible) outcome.

One-upper是这样一种人：在听完别人的经历或问题后，马上就会分享自己的一个相似的故事，但结局总要比前面那个人说的故事精彩（或糟糕）得多。这种人相当令人讨厌。

One-upper is one who feels like they need to be better than everyone else, so they constantly "one-up" anything that anyone says.

One-upper觉得自己必须比其他任何人都要好，所以不管别人说什么，他们总要压人一头。