The idiom 'the elephant in the room', refers to a serious problem or situation which is perceived and noticed by everyone but not spoken about due to fear of awkwardness inability to address the issue or fear of embarrassment. The elephant in the room refers to something obvious that is not addressed.

1. When I dropped out of college, my parents didn't say anything to me about it, but soon it reached a point where we needed to address the elephant in the room and sort things out.
2. Can we discuss the obvious elephant in the room? I'm concerned about your ability to pay for the apartment when you are not in a full-time job?.

1. In the meeting, we discussed the tasks to be completed that day, totally ignoring the elephant in the room which was the impending takeover of the company.
2. Helen's resignation was the elephant in the room, but everyone at the office chose to ignore it in case it landed them in trouble with management.