1. That moment of the day that divides the daylight hours for that day exactly in half. To determine solar noon, calculate the length of the day from the time of sunset and sunrise and divide by two. Solar noon may be quite a bit different from 'clock' noon.
2. The local time when the sun is closest to its zenith.
https://www.solar-electric.com/learning-center/general-solar-information/photovoltaic-solar-power-glossary.html (1.); http://www.yourdictionary.com/solar-noon (2.)