- the middle of summer.
- the summer solstice, around June 21.
- the middle or height of the summer
- (as modifier)a midsummer carnival
- another name for summer solstice
n.Old English midsumor, from mid + sumor “summer” (see summer (n.1)). Midsummer Day, as an English quarter-day, was June 24. Astronomically June 21, but traditionally reckoned in Europe on the night of June 23-24.