Infrared

a.	1.	(Physics) Lying outside the visible spectrum at its red end; - said of rays having a longer wavelength (and thus less refrangible) than the extreme red rays, specifically those electromagnetic waves having a wavelength of between 700 nanometers and 1 millimeter.
	2.	relating to, using, or producing infrared radiation.
	3.	affected by infrared radiation; as, infrared detector; infrared film.

Noun	1.	infrared - the infrared part of the electromagnetic spectrum; electromagnetic wave frequencies below the visible range; "they could sense radiation in the infrared" Synonyms: infrared frequency
	2.	infrared - electromagnetic radiation with wavelengths longer than visible light but shorter than radio waves Synonyms: infrared emission, infrared light, infrared radiation
Adj.	1.	infrared - having or employing wavelengths longer than light but shorter than radio waves; lying outside the visible spectrum at its red end; "infrared radiation"; "infrared photography"

(electronics)

infrared - (IR) Electromagnetic waves in the frequency range just below visible light corresponding to radiated heat. IR waves can be generated by a kind of LED and are often used for remote controls for televisions etc. and in some docking stations.

invisible, unseeable