(of electromagnetic radiation) having a wavelength just greater than that of the red end of the visible light spectrum but less than that of microwaves. Infrared radiation has a wavelength from about 800 nm to 1 mm, and is emitted particularly by heated objects.
(of equipment or techniques) using or concerned with infrared radiation:infrared cameras
the infrared region of the spectrum; infrared radiation.
infrared in other Oxford dictionaries
Definition of infrared in the US English dictionary