1. longest or shortest day: either of the times when the Sun is farthest from the equator, on or about June 21 or December 21. The summer solstice falls in June in the northern hemisphere but in December in the southern hemisphere, and vice versa for the winter solstice.
2. point on ecliptic: either of the two points on the ecliptic when the Sun reaches its northernmost or southernmost point relative to the celestial equator
[13th century. Via French< Latin solstitium< sol "Sun" + stit-, past participle of sistere "stand still"]
