elephant
the elephant in the corner (or room) an embarrassing or awkward topic that everyone is aware of but no one wishes to discuss.
2003CNN Of course, the elephant in the corner for all these developments is Yasser Arafat, the chairman of the Palestinian Authority.
2004New York Times When it comes to the rising price of oil, the elephant in the room is the ever-weakening United States dollar.
see the elephant see the world; get experience of life. US
☞ An elephant is used here to symbolize or typify something which is extremely remarkable or exotic.
2003Boston Review His experience [during World War I] as a pilot was limited to a few practice flights in Canada, and the war was over before his squadron had a chance to go see the elephant in the sky above Verdun.
a white elephant: seewhite.