Nouns

(n)infrared, infrared frequencythe infrared region of the electromagnetic spectrum; electromagnetic wave frequencies below the visible range“they could sense radiation in the infrared”
(n)infrared, infrared light, infrared radiation, infrared emissionelectromagnetic radiation with wavelengths longer than visible light but shorter than radio waves

Adjectives

(s)infraredhaving or employing wavelengths longer than light but shorter than radio waves; lying outside the visible spectrum at its red end“infrared radiation”, “infrared photography”