The Collaborative International Dictionary of English v.0.48:

Infrared \In`fra*red"\, Infra-red \In`fra-red"\, a. [Infra- +
   red.]
   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.
      [Webster 1913 Suppl. +PJC]

   2. relating to, using, or producing infrared radiation.
      [PJC]

   3. affected by infrared radiation; as, infrared detector;
      infrared film.
      [PJC]

WordNet (r) 3.0 (2006):

infrared
    adj 1: 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"
    n 1: the infrared region of the electromagnetic spectrum;
         electromagnetic wave frequencies below the visible range;
         "they could sense radiation in the infrared" [syn:
         infrared, infrared frequency]
    2: electromagnetic radiation with wavelengths longer than
       visible light but shorter than radio waves [syn: infrared,
       infrared light, infrared radiation, infrared emission]

The Free On-line Dictionary of Computing (30 December 2018):

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.

   (1997-01-30)