1. Either of the two points on the ecliptic midway between the equinoxes, at which the sun is at its greatest angular distance north (summer solstice) or south (winter solstice) of the celestial equator.

2. The time at which the sun reaches either of these points. The summer solstice occurs on June 21 and the winter solstice on December 21 in the northern hemisphere; the dates are reversed in the southern hemisphere.