D defs.my
Entry 1 sense Webster, 1913

damper

/(dăm"pẽr)/ · damp·er · IPA /ˈdæmpɚ/
01 n. That which damps or checks;
  1. 1.
    That which damps or checks;
    “Nor did Sabrina's presence seem to act as any damper at the modest little festivities.” — W. Black.