Unabridged means a book, speech, recording, or document is given complete — nothing has been cut out to make it shorter. The word almost always appears where a shorter version also exists, and it is there to promise you that this is not that shorter version. You meet it on book covers ('the unabridged edition'), on audiobooks ('unabridged, 32 hours'), on dictionaries (an unabridged dictionary is the giant one that tries to include every word, not the desk-sized one), and on recordings of speeches or interviews. Because of that, unabridged is really a marketing word as much as a describing word: it is a seller telling a buyer 'you are getting all of it.' It is formal and written; nobody says it about a conversation or a film. Note that unabridged is not the same as uncut or uncensored — an unabridged text can still have been edited for grammar, or published with a translator's changes, or exist in only one version and simply never have been shortened. It only tells you about length, not about faithfulness in every other way. Occasionally people stretch it for effect, as in 'the unabridged version of what happened last night', meaning the long story with nothing left out; that use is playful and borrowed from books. It works only before a noun or after the verb be; there is no verb 'to unabridge'.