humorous someone who spoils other people's enjoyment of social activities by being unhappy or by refusing to become involved.
Tim called me a party pooper because I left the party just after midnight.
party pooper
⇨ party pooper; party poopnoun a killjoy; a spoilsport US, 1954
party pooper
A person who dislikes or refuses to participate in social events, often with the result of detracting from others' enjoyment of such events. Amy is such a party pooper. She thinks our company's social functions are stupid and just stands around pouting the whole time.Don't be a party pooper, come and talk to the rest of us!
party-pooper
n. the first person to leave a party; someone who ruins a party because of dullness or by leaving early. Don’t invite Martha. She’s such a party-pooper.