This expression means to discourage. This modern meaning is in use since the beginning of the nineteenth century, even the expression in the sense of 'to slander' goes back to the Roman playwright Plautus. The origin is unknown, but the phrase probably alludes to the dousing of brawling cats and mating dogs in cold water, thus bringing their intentions to an abrupt end.

Übersetzung:

jemandem eine kalte Dusche verpassen

Gegenteil(e)

The opposite of "to pour/throw cold water on somebody's plans" is "to give somebody a boost".

Synonym(e):

You could also say: to quench enthusiasm.