https://www.abc10.com/article/news/nation-world/merriam-webster-new-words-september-2019/103-cec4a002-959f-4909-ae9b-846f781f47d3

WASHINGTON — It was announced with a tweet. You can now feel comfortable telling your friends to be careful with what they flush, or else they'll cause a "fatberg." 

The Merriam-Webster dictionary now defines this noun as a "large mass of fat and solid waste that collects in a sewer system."

The word is timely considering the rising popularity of moist towelettes and so-called "flushable" wipes, the varieties seem to be endless. They're apparently a nightmare for New York sanitation workers who don't find them "flushable" at all.