찬물을 끼얹다 (chan-mu-reul ggi-eon-da) – pour cold water on/throw a wet blanket/discourage
The definition is pretty straightforward but let’s break it down so that it makes more literal sense, at least.
찬물 = cold water (찬 means cold and 물 means water)
끼얹다 = to pour (something)
찬물을 끼얹다 can be translated to be “throw a wet blanket” too.
To pour cold water or to throw a wet blanket means to be pessimistic about something or to be a spoilt sport. Basically being the one to reject an idea or say no when everyone else is agreeable.
엄마가 빨리 자라고 해서 파티에 좀 찬물을 끼얹었어.
My Mum told us to quickly go to bed so it was a wet blanket/she poured cold water on us.