Meteor is in game for sure, currently as a black magic lv200 with 1 mana cost. Some jpn scanned the db and found a list of "hidden" spells. Too bad I forgot the url about this...
Meteor and Meteor II are in the game's data, but not Ultima (yet). So far Meteor is useable by monsters only. It's been arbitrarily set to max level (200) for BLM with an MP cost of 1.
If you want to see Meteor in action, just do a /sea on Behemoth's Dominion every once in a while. If you see a large number of high level people there, head out there and check out the fight. Take care, though...