Moderately formal: a semiformal dance. (adjective)
Suitable or appropriate for a moderately formal occasion: semiformal attire. (adjective)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "semiformal" in a sentence
"From TJ! with his own street cart!) to cook and serve authentic street tacos for a hundred-odd adults in semiformal wear."
"Except at the very end of C&A, when a cleaned-up Ford, in semiformal cowboy wear a shout out to my friend Roger Ebert complete with oddly banded cowboy hat, positively beams as he tries to take Daniel Craig's hat off to uncover his rumored forehead and eyebrows and is shot dead by Deadly Dan for his temerity."
"The social calendar of Kappa Kappa Gamma sorority members at the University of Georgia holds about 10 formal or semiformal events per semester."