A kill-joy is someone who ruins the fun for everyone else. Synonyms for this term include spoilsport, party pooper, wet blanket, buzzkill, and stick-in-the-mud. A spoilsport is someone who ruins an event or activity by either not participating or by having a negative attitude. A party pooper is someone who spoils the enjoyable atmosphere of a party. A wet blanket is someone who dampens the spirits of others, making them feel disappointed or unhappy. A buzzkill is someone who stops the party or enthusiasm. A stick-in-the-mud is someone who is seen as boring and stuck in their ways. All of these synonyms are used to describe someone who puts a damper on the enjoyment of others.