1. the time at which the sun is at its northernmost point in the sky (southernmost point in the S hemisphere), appearing at noon at its highest altitude above the horizon. It occurs about June 21 (December 22 in the S hemisphere)
2. (astronomy) the point on the celestial sphere, opposite the winter solstice, at which the ecliptic is furthest north from the celestial equator. Right ascension: 6 hours; declination: 23.5°