One who dampens fun; one who declines to participate in a group activity; one who does not agree with the opinions of a group
Still, it's not something that any country can easily walk away from—not even a Bush administration that has made a habit of being the party pooper in international forums.
disapproval You describe someone as a party pooper when you think that they spoil other people's fun and their enjoyment of something. I hate to be a party pooper, but I am really tired. someone who spoils other people's fun