party pooper

[poo-per] /ˈpu pər/
noun, Slang.
1.
a person who hasn't the interest or vitality to participate actively in a social party and whose mood, attitude, or personality lessens others' enjoyment; killjoy.
Also called poop.
Origin
1940-45; poop2 + -er1
British Dictionary definitions for party pooper

party pooper

/ˈpuːpə/
noun
1.
(informal) a person whose behaviour or personality spoils other people's enjoyment
Word Origin
C20: originally US
Slang definitions & phrases for party pooper

party pooper

noun phrase

A morose, pessimistic person; killjoy, wet blanket: No one can call Mr Bulganin and Mr Kruschchev party poopers/ What a party poop you are today, Sally (1951+)