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.
Human and rat retinas have two types of light receptors: cones are sensitive to bright light and color, and rods are sensitive to dim light and cannot see color. Human and rat retinas differ, however, in the types and density of cones in the retina, which has implications for color vision.