buzzer

when something or someone ruins an activity, etc.
a cross between buzz kill and bummer

me: i was going to go to the beach today, but now its raining.

you: aww man, thats a buzzer!

me: we were having a great time shopping but then becky showed up.

you: wow, that sucks, she's such a buzzer!

by lisabisa April 15, 2011