Definition of partial solar eclipse. : an eclipse of the sun in which the moon does not completely hide the solar surface or photosphere so that some direct rays of sunlight reach the observer : all the part of a totalsolar eclipse outside of the path of totality.
A partial lunar eclipse occurs when the Earth moves between the Sun and Moon but the 3 celestial bodies do not form a perfectly straight line in space. When that happens, a small part of the Moon's surface is covered by the darkest, central part of the Earth's shadow, called the umbra.