The elephant in the room
Definition 1 of 1
Pro Tip 1/3Emotional Weight
Using this phrase can indicate a serious, uncomfortable issue that affects everyone's feelings in the situation. 
During the family dinner, the elephant in the room was Uncle Joe's recent job loss.
Pro Tip 2/3Conversation Starter
Bring up the elephant in the room to openly discuss something that people may be avoiding. 
Let's address the elephant in the room: we need to talk about the budget cuts.
Pro Tip 3/3Cultural Sensitivity
Some cultures may find talking about the 'elephant in the room' more challenging due to norms around politeness or confrontation. 
He was hesitant to mention the elephant in the room during the international meeting.