(physics) Light (or other electromagnetic radiation) whose electric or displacement vector rotates in a plane perpendicular to the propagation direction with constant angular velocity

circularly polarized light

(physics) polarized light in which the electric and magnetic fields vibrate in same phase

(Australia) An unexplained light reportedly appearing in the sky in remote parts of Australia, especially northwest Queensland, possibly caused by reflections of distant light in the dry air conditions.

(physics) A rectifying semiconductor device which converts electrical energy into electromagnetic radiation of a wavelength in or near the visible spectrum of light.

Any joke of the form "How many X does it take to change a light bulb?" followed by a witty riposte, where X is some usually stereotypical class of people.

An area of a town where prostitution is concentrated.

(physics) any optical method used to measure the extent of the scattering of light by suspended particles or by macromolecules

(idiomatic) To manage something without difficulty.

A system that uses traffic-light colours to indicate how widely information or sensitive documents can be shared.