a measure of the ability of a material or medium to transmit electromagnetic energy, as light.
Origin of transmissivity
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
physics a measure of the ability of a material to transmit radiation, equal to the internal transmittance of the material under conditions in which the path of the radiation has unit length
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