(countable) A light bulb that emits ultraviolet light, usually used to create the illusion that anything white is glowing. / (uncountable, slang) ultraviolet radiation/light

A source of illumination.

Ground combat soldiers who are not mechanized, and whose role is to harass the enemy in front of the main body of infantry.

(astronomy, idiomatic, informal) A reflecting telescope, especially one with a relatively large aperture and suitable for observing deep sky objects such as nebulae and galaxies.

(cricket) The lighter of the rollers used for flattening the pitch between innings.

synchrotron radiation

A traffic light in its green state (indicating that vehicles may proceed). / (idiomatic) Approval, or permission to proceed.

(physics) The part of the electromagnetic spectrum, between infrared and ultraviolet, that is visible to the human eye.

(uncountable) Light, having a mixture of frequencies, being perceived as having no specific colour; such as sunlight. / (countable) A white-coloured light or lamp

(physics) light in which the electric and magnetic fields each vibrate in a single plane