Oh boy, 1000 new words!

The popular (American) English dictionary, Merriam-Webster just announced their approval of 1000 new words or meanings added to their dictionary.

https://www.merriam-webster.com/words-at-play/new-words-in-the-dictionary-feb-2017

The Oxford English Dictionary adds new words and entries quarterly. So you may see some words in some dictionaries, and not in others. Most dictionaries discretely and quietly remove words too, but not the full OED. It keeps everything from the first edition on. But it's not on-line.

If you are reading classical literature, it is useful to refer to old dictionaries such as Webster's 1828 and 1913 editions. It's curious that the word "thrave" is in the newer edition, but noted as obsolete in the older one.

The link to Webster's old edition in this cross-dictionary lookup site is broken.