wet blanket
US /wɛt ˈblæŋkɪt/
UK /wɛt ˈblæŋkɪt/

1.
興ざめな人, 水を差す人
a person who spoils other people's fun by being negative and unenthusiastic
:
•
Don't invite John to the party; he's such a wet blanket.
ジョンをパーティーに誘わないで。彼は本当に興ざめな人だから。
•
She's always being a wet blanket, complaining about everything.
彼女はいつも興ざめな人で、何にでも文句を言う。