空気読む
Kuukiyomu
くうきよむ
'Kuuki' (air/atmosphere) + 'yomu' (to read) means picking up on the unspoken mood of a situation and behaving appropriately. This is a hugely valued social skill in Japan. Someone who can't do this was once labeled 'KY' (kuuki yomenai, 'can't read the air'), a buzzword from around 2007, though 'KY' itself is rarely used today. 'Kuuki yome' ('Read the room!') is a warning not to disrupt the group harmony. The 'air' here carries a nuance of expected consensus, not just general atmosphere.
Examples
あいつマジで空気読めないよな。みんな帰りたがってるのに気づかない
That guy seriously can't read the room. Everyone wants to go home and he doesn't even notice.
Talking with a friend after a drinking party
空気読んで静かにしてくれない？
Can you read the room and keep it down?
Telling a noisy colleague to be quiet during a meeting
日本で働くなら空気を読む力が大事だよ
If you're going to work in Japan, the ability to read the room is essential.
空気読みすぎて自分の意見が言えない
I read the room so much that I can never say what I actually think.