Humbedooh wrote:I'd be so bold as to say Oxford is a soddy old bum then ;p or the likes. I suppose they'll accept "internal / outternal" as well soon?

(better go check, hmm..).
LOL.
They've probably included it, because many people use it today, but regardless of how many people say "outro", it's still wrong in the sense, that it makes people think it has to do with the english terms in/out, which is not the case (my own musical education was purely classical, so I've dealt with many ex/introitae, and woe to those that called it out instead of ex ;p).
Debates over whether words that aren't "correct" in an etymological sense are "really" words have and will continue to occur; besides, English is already one big mess.
From my POV, though, what's important is the meaning of the word is clear, and that it doesn't confuse or obfuscate reality. In this case, I don't know that "outro" could be taken to mean anything else or confuse anything else!
On the other hand, a word like "remix" is misleading, because typically a "remix" is a complete rearrangement of the track, and sometimes has almost nothing to do with the original. Everyone knows this, of course, but it confuses the word "mixing" which strictly means the job of the guy sitting at the mixing console. Unfortunately we're stuck with it since from a marketing point of view it would be foolish to use any other word.
Anyway, what to use here... well, I can say I've never heard the word "extro". OK, let's check the textbooks... how about "ending"?