Killjoy noun
A person who stops other people from enjoying themselves or having fun.
I don't want to be a killjoy, but we will have an exam tomorrow morning.
Mary is called a killjoy just because she often refuses to drink alcohol in a party
The plural form of "killjoy" is "killjoys".
The noun dates from 1776.
Used to describe someone or something that is very cool or good
Wow, your cap is really funky fresh.