Meaning
A major problem or controversial issue that is obvious to everyone, but nobody wants to talk about it.
Origin
Became popular in the 1950s. If an elephant were in a room, it would be impossible to ignore, so ignoring it is a conscious choice.
Example Sentence
"We need to discuss the elephant in the room: the company is running out of money."
Synonyms
unspoken issue
obvious problem
taboo topic