adj. Bearing some but not all the power of being official. As a semioffical opinion that is offered as probably correct and accurate but may be overturned on review and replaced by an official statement.
the GNU version of the Collaborative International Dictionary of English
adj. Half official; having some official authority or importance.
The Century Dictionary and Cyclopedia
Partly official; having some degree of official authority; made upon information from those who have official knowledge: as, a semi-official confirmation of a report; a semi-official organ.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
adj. having some official authority or sanction
Word Usage
"Unfortunately, the consequence was, that I did not understand a word that was said at dinner -- a kind of semiofficial reception."