unholiday adjective 1noun 1forms 3 adjective1 •Grim or drab; the antithesis of festive.O that unholiday look of English countenances, how sad it is! — 1856 noun1 •A day or period of time which is not a holiday, but is celebrated as if it were one.Yet the most touching gifts are often the ones that come as unbirthday or unholiday or unanniverary gifts. — 2013 formsunholidays · more unholiday · most unholiday