The point in the sky directly opposite the sun, or a phenomenon where light appears to come from the opposite direction of the sun.
From counter- (against, opposite) + sun. The prefix counter- comes from Latin contra- meaning 'against.' This term emerged in astronomy to describe optical phenomena where light scattering creates the illusion of a secondary sun.
The countersun is actually related to the mysterious 'glory' effect you sometimes see from airplanes—when your plane's shadow is surrounded by a rainbow halo. It's the same optical trickery that made ancient peoples think there were ghost suns in the sky!
Complete word intelligence in one call. Free tier — 50 lookups/day.