KY
Keーwai
けーわい
An abbreviation of 'Kuuki (ga) Yomenai' — literally 'can't read the air.' It was nominated for Japan's Buzzword of the Year in 2007. Used to describe someone who ruins the vibe with poorly timed comments or actions. It was huge at the time, but by 2025 younger people consider it a bit dated. Not used that much anymore in practice.
Examples
あの人KYだから、空気凍ること多いんだよね
That person is so KY — they freeze the room all the time.
Talking with friends about a mutual acquaintance
自分がKYなの分かってるから、発言する前に考えるようにしてる
I know I'm KY, so I try to think before I speak.
Talking about self-awareness
KYって言葉、最近あんまり聞かなくなったね
You don't really hear 'KY' much anymore, do you?
KYな発言して場が静まった
I made a KY comment and the whole room went silent.