Complex sentence: Elephant in the room or Elephant in the living room is an English metaphorical idiom for an obvious problem or risk no one wants to discuss, Cambridge University Press.
Split into simpler sentences: Elephant in the room or Elephant in the living room is an English metaphorical idiom for an obvious truth that is going unaddressed. The idiomatic expression also applies to an obvious problem or risk no one wants to discuss, Cambridge University Press.