Midsummer Day Syllabification: (Mid·sum·mer Day) (also Midsummer's Day)Translate Midsummer Day | into French Definition of Midsummer Day noun (in England, Wales, and Ireland) June 24, originally coinciding with the summer solstice and in some countries marked by a summer festival. Midsummer Day in other Oxford dictionaries Definition of Midsummer Day in the British & World English dictionary