The phrase "taboo thing" refers to a topic or subject that is considered socially unacceptable or forbidden, often because it violates moral, cultural, or religious norms. Full definition
It's one of the most taboo things in the world yet a huge part of life for half the people on this planet. (visualnews.com)
So well written because they discuss some pretty taboo things but it shows you a different point of view. (goodreads.com)
If only solution would require such taboo thing, then the easiest thing is to assume that the problem simply do not exist. (politics.stackexchange.com)