sb who spoils other people´s enjoyment of something by refusing to join in an activity
We were all having a good time until Harold walked in and started acting like a wet blanket. Google
Hating to resemble a wet blanket he held his peace. BNCI
But I haven't done anything --; except be an absolute misery,'; she added honestly as she realised for perhaps the first time what a wet blanket she had been. BNCI
The morose Mitchells wins the wet blanket award. BNCI