the elephant in the room

US /ðɪ ˈɛlɪfənt ɪn ðə ruːm/
UK /ðɪ ˈɛlɪfənt ɪn ðə ruːm/
"the elephant in the room" picture
1.

房間裡的大象, 顯而易見卻無人提及的問題

an obvious problem or difficult situation that people do not want to talk about

:
Everyone knew about the company's financial troubles, but no one dared to address the elephant in the room.
所有人都知道公司的財務困境,但沒人敢提及房間裡的大象
Their strained relationship was the elephant in the room during the family dinner.
他們緊張的關係是家庭晚餐時房間裡的大象