from The American Heritage® Dictionary of the English Language, 4th Edition
- adj. Moderately formal: a semiformal dance.
- adj. Suitable or appropriate for a moderately formal occasion: semiformal attire.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- adj. Somewhat formal.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- adj. moderately formal; requiring a dinner jacket
semi- + formal (Wiktionary)