What is "eikonal"

a. (context physics mathematics English) Describing the properties of a class of partial differential equation encountered in descriptions of wave propagation.

Eikonal is the German form of the Greek word εἰκών, meaning likeness, icon or image. It can refer to:

• Eikonal equation, a non-linear partial differential equation encountered in problems of wave propagation.
• Eikonal approximation, a method of approximation useful in wave scattering equations.
• Operation Eikonal, an operation conducted by the National Security Agency in collaboration with the Bundesnachrichtendienst