Princeton's WordNet(0.00 / 0 votes)Rate this definition: 1  shimmer, play(verb) a weak and tremulous light. 2  shimmer(verb) shine with a weak or fitful light. 3  shimmer(verb) give off a shimmering reflection, as of silk.
Cats, like humans, have both rods and cones in the retina. Rods are the receptors that the eye uses for night time viewing and sudden movement. Cones are used during the daytime, and process color information. Cats have more rods than cones, as compared with humans, making cat night vision superior to humans.
Rods are important for seeing black, white, and gray; cones are the receptors responsible for color vision, and are separated into three types: red-sensitive, green-sensitive, and blue-sensitive. In order to see all the colors of the rainbow, combinations of these three color receptor cones must be activated simultaneously.