What is the defination of Pointing Loss in terms of Free Space Optical communications?

Answer 1

If you point optical system in the wrong direction, it misses the target, or partly misses it.

Assume you want to transmit power by laser. You build a powerful laser to shine a bright light on a distant solar panel. The light from the laser provides power to the solar panel only if the light actually hits the solar panel. If you point the beam in the wrong direction, the beam may completely miss the solar panel, which is 100% pointing loss. Or if your aim is pretty good but not perfect, maybe half the beam hits the solar panel and half misses, in which case your pointing loss is 50%.