from The American Heritage® Dictionary of the English Language, 4th Edition
- adj. Not official: the unofficial election results.
- adj. Not acting officially: an unofficial adviser.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- adj. Not officially established.
- adj. Not acting with official authority.
- adj. Not listed in a national pharmacopeia &c.
from The Century Dictionary and Cyclopedia
- Not official; specifically, in medicine, not approved by an authoritative body.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- adj. not having official authority or sanction
- adj. not officially established
un- + official (Wiktionary)