To discourage or deter something; to make something less enjoyable, pleasant, or fun; to extinguish or lessen people's enthusiasm for something. (A less common variant of "put a damper on something.") The foul weather really put the damper on our picnic yesterday. Without question, this tax scandal has put the damper on the senator's likelihood of being re-elected. CDs quickly became the dominant format for music, but when digital formats arrived soon thereafter, it put the damper on CD sales just as quickly.