WOW: There are about 2 meanings that are most common: "a sudden expression of an emotion in your eye" and "something that is thought about or planned but not yet started."
When someone has a gleam in their eye, it means they have a noticeable sparkle or brightness in their eyes, often indicating excitement, enthusiasm, or mischief.
The gleam in your eye can be sparked by something that excites or inspires you.
There was a gleam in his eye.
His expression was one of surprise and curiosity when he saw the gleam in her eye.
Hitting pay dirt puts a certain gleam in a man's eye.
Because the first film starts with a gleam in the eye of the producer(s) or the director. The sequel starts with a gleam in the eye of the finance department of the studio or its shareholders.
happening quickly
An idiom is a phrase that seems to make no sense unless you know the definition. This makes sense, so it is not an idiom. Something caught the gleam of light from a shiny object.
"Gleam" may be used as a noun to denote an indistinct light stream or indistinct observation of another object. As a verb, "gleam" can mean a gentle, not profound, shine or glisten.
The glint of excitement in his eye was noticeable due to the sparkle and brightness that appeared when he talked about the topic.
Stars gleam in the sky Diamonds gleam in the light.
"Albedo" and "reflection", or perhaps "glare", "gleam", or "glimmer" refer to the light reflected from a smooth surface. I am not sure what you mean by the second half of your question however.