To dampen something such as someone's enthusiasm or excitement means to make it less lively or intense.
例句
Nothing seems to dampen his perpetual enthusiasm...似乎没有什么能让他那持久的热情消退。I hate to dampen your spirits but aren't you overlooking a couple of minor points.我不想扫你的兴，但你是否忽视了几个小的问题呢？
VERB
使潮湿;弄湿
If you dampen something, you make it slightly wet.
例句
She took the time to dampen a washcloth and do her face.她花了点时间弄湿毛巾，洗了把脸。