How to call a Buzz Killer in Korean?

When we hang out with our friends, 

there's always a person who kills the mood 

by speaking random subjects or acting weird.

In Korean, this buzz killer is called

갑분싸

[Gapbunssa]

갑자기 분위기 싸해진다.

Suddenly, the ambiance turns cold.

갑분싸 is an acronym of this Korean phrase

to describe the situation that the ambiance 

turns cold and awkward.