Definition: (concerning eyes) to become dull and blank.
(This phrasal verb has more than 1 meaning)
E.g.1: He knew his students were bored because their eyes had clouded over and some of them were beginning to doodle in their notebooks.
E.g.2: At the end of the film, after the hero had rescued everyone he fell to the ground, his eyes clouded over, he twitched and then died.
This phrasal verb cannot be separated.