Basic Definition: "Cold water" generally refers to water that is at a low temperature. However, in a figurative sense, it can mean to discourage or dismiss an idea, plan, or hope. In this context, when someone "pours cold water" on something, they are expressing doubt or negativity about it.
In advanced conversations, "pouring cold water" can be used in discussions about projects, dreams, or plans. It implies that someone is being realistic or practical, but it can also come off as discouraging.
In summary, "cold water" can be both a literal term for water that is cold and a figurative expression used to describe discouraging someone's plans or hopes.