What is "debbie downer"

n. (context informal pejorative English) A naysayer; one whose negative remarks depress or dissuade others.

Debbie Downer is a name of a fictional Saturday Night Live character who debuted in 2004, and who was portrayed by Rachel Dratch.

The character's name, Debbie Downer, is a slang phrase which refers to someone who frequently adds bad news and negative feelings to a gathering, thus bringing down the mood of everyone around them. Dratch's character would usually appear at social gatherings and interrupt the conversation to voice negative opinions and pronouncements. She is especially concerned about the rate of feline AIDS, a subject that she would bring up on more than one occasion saying it was the number one killer of domestic cats.