dampen down

1. To make a place or thing wet, especially in order to prevent, halt, or extinguish a fire. A noun or pronoun can be used between "dampen" and "down." The flames may be under control, but if we don't dampen down the burnt materials and eliminate hot spots, it could start up again soon. The fire was mostly contained by 5 AM, with firefighters dampening the remaining areas down by 6. Quick, dampen down the flames while they're still contained to one pot!

2. To have a stifling, subduing, or deadening effect on something, such as an action or emotion. A noun or pronoun can be used between "dampen" and "down." The Federal Reserve's announcement seems to have dampened down the economy's recent growth. Hearing more details about the project certainly dampened my enthusiasm down for it. Activists fear that this latest legislation will effectively dampen down free speech.