The wordsmiths at the Springfield, Mass.-based dictionary publisher say they picked the new entries after monitoring their use over years.
"As soon as we see the word used without explanation or translation or gloss, we consider it a naturalized citizen of the English language," said Peter Sokolowski, an editor-at-large for Merriam-Webster. "If somebody is using it to convey a specific idea and that idea is successfully conveyed in that word, it's ready to go in the dictionary."
Many of the new entries reflect the nation's growing interest in the culinary arts, including prosecco (a sparkling Italian wine) and soju (a Korean vodka distilled from rice). Others define new technology or products, such as infinity pool - an outdoor pool with an edge designed to make water appear to flow into the horizon.
Others reflect current events and much-discussed news topics, including dirty bomb (a conventional bomb that releases radioactive material) and Norovirus (small, round single-stranded RNA viruses, such as the Norwalk Virus).
And then there's "mondegreen." In a category of its own, it describes words mistaken for other words.
A mondegreen most often comes from misunderstood phrases or lyrics. It comes from an old Scottish ballad in which the lyric "laid him on the green" has been confused over time with "Lady Mondegreen."
Among the best-known modern examples: "There's a bathroom on the right" in place of Creedence Clearwater Revival's "There's a bad moon on the rise" and " 'Scuse me, while I kiss this guy" in place of "kiss the sky" in the 1967 Jimi Hendrix classic "Purple Haze."
Even Sokolowski, a word specialist by trade, has a favorite mondegreen: "Lucy in the sky with diamonds," as sung by the Beatles in 1967, made sense to the preteen Peanuts comic fan as "Lucy in the sky with Linus."
Merriam-Webster's editors were so amused by the mondegreen concept that they plan to ask people to submit their favorites on the publishing company's website.
Mondegreen, first spotted in print in 1954, was among tens of thousands of words the wordsmiths watched for decades. That and others make the cut for the dictionary based on how widely they are used in publications ranging from newspapers to technical manuals.