damper

Concise Oxford English Dictionary © 2008 Oxford University Press:
damper/ˈdampə(r)/

▶noun

• 1 Music a pad that silences a piano string except when it is removed by means of a pedal or by the key being struck.

• 2 a device for reducing vibration or oscillation.

• 3 a movable metal plate in a flue or chimney, used to regulate the draught and so control the rate of combustion.

• 4 chiefly Austral./NZ an unleavened loaf or cake of flour and water baked in wood ashes. [in the sense ‘something that takes the edge off the appetite’.]

– phrases
put a damper on have a subduing or inhibiting effect on.