a green coloration of the upper portion of the sun, caused by atmospheric refraction and occasionally seen as the sun rises above or sinks below the horizon.
Origin of green flash
First recorded in 1910–15
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
astronomy a flash of bright green light sometimes seen as the sun passes below the horizon, caused by a combination of the dispersion, scattering, and refraction of light
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012