The term refers to a question, problem, solution, or controversial issue which is obvious to everyone who knows about the situation, but which is deliberately ignored because to do otherwise would cause great embarrassment, sadness, or arguments, or is simply taboo. The idiom can imply a value judgment that the issue ought to be discussed openly, or it can simply be an acknowledgment that the issue is there and not going to go away by itself.

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The term is often used to describe an issue that involves a social taboo or which generates disagreement, such as race, religion, politics, homosexuality, mental illness, or suicide. It is applicable when a subject is emotionally charged, and the people who might have spoken up decide that it is probably best avoided.

The idiom is commonly used in addiction recovery terminology to describe the reluctance of friends and family of an addicted person to discuss the person's problem, thus aiding the person's denial. Especially in reference to alcohol abuse, the idiom is sometimes coupled with that of the pink elephant, “the pink elephant in the room.”