Green’s Dictionary of Slang

1. an unpleasant experience or event that destroys one’s peace of mind or enjoyment, also attrib.

1987		Eble Campus Sl. Spring 2: buzz stomp – someone or something that puts a damper on a good atmosphere: The rain put a buzz stomp on our evening.
1997–2002		Hope College ‘Dict. of New Terms’ 🌐 buzz kill A phrase used to describe something that gets in the way of a person or group of people trying to have fun. Can sometimes take on the form of a noun, when an actual person is the damper to the others’ good times. [...] ‘That was such a buzz kill when the police showed up at the party.’ ‘Don’t invite her, she’s always a buzz kill.’.
2020		C. Hiaasen Squeeze Me 237: He said sitar music was a buzzkill.
2020		NY Rev. Bks 17 Dec. 🌐[T]he author characterizes issues affecting the poor—housing and health care [...] and food insecurity—as ‘buzz-kill’ issues.

2. an unpleasant person, esp. one who ruins a hitherto enjoyable time.

1989		P. Munro Sl. U.
1997–2002		see sense 1.
2012		Slate 21 Nov. 🌐 Let me say at the outset, I don’t mean to be a buzz-kill. I’m happy for you if you like white-meat turkey.
2017		J.R. Lawrence My Camp 116: He should have been called Sgt Buzzkill, he really was a joyless, empty man.
2020		C. von Ziegesar Cobble Hill 261: She sounded happy. Liam didn’t answer. He didn’t want to be a buzzkill .