The Oxford English Dictionary (OED) does not generally add new words into the printed dictionary until they have had some time to become established. In the meantime they are added to the online version, launched on 14 March 2000.
Some examples of new words added to OED online in the twenty-first century are: sext (2001), staycation (2005), crowdfund (2008), photobomb (2008). You might be excused for thinking that the word twerk, associated with Miley Cyrus’s sexually provocative dance routine in 2013, was another new word but it has a longer history. In the early 1990s ‘twerk’ was used in the New Orleans hip hop music scene, and known as ‘bounce’, to describe dancing that emphasized the dancer’s backside. Before that its use is thought to date back another 170 years to the 1820s, when it was spelt as ‘twirk’ and used as a noun to describe a twitching or jerking movement. Although its precise origin is not known for sure, it could be a combination of ‘twitch’ and ‘jerk’.
Some recent but lesser known new words are:
choss used in rock climbing and mountaineering to refer to crumbly or loose rock considered unsafe to climb, but also used by the author of Gone With the Wind, Margaret Mitchell, in a letter as a humorous version of the word chaos in her household due to workmen.
freegan, being a blend of free and vegan, to refer to someone who eats discarded food from supermarkets and restaurants for environmental reasons.
intersectionality has its origins in mathematics, but has been more recently used to describe the interconnections between various social categorizations such as class, gender and race, often with regard to disadvantage and discrimination.
meh, an expression to convey indifference, probably popularized by TV series The Simpsons.
English is an ever-changing and evolving language.