Infrared radiation

Infrared (IR) radiation is  electromagnetic radiation of a wavelength longer than that of visible light, but shorter than that of radio waves. The name means "below red" (from the Latin infra, "below"), red being the color of visible light with the longest wavelength. Infrared radiation has wavelengths between about 750 nm and 1 mm, spanning five orders of magnitude.
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Radiation /ra·di·a·tion/ 1. divergence from a common center. 2. a structure made up of divergent elements, as one of the fiber tracts in the brain. [more]Infrared radiation - Community and Resources

Noun
1. electromagnetic radiation with wavelengths longer than visible light but shorter than radio waves
(synonym) infrared, infrared light, infrared emission
(hypernym) actinic radiation, actinic ray

The heat energy that is emitted from all solids, liquids, and gases. In the context of the greenhouse issue, the term refers to the heat energy emitted by the Earth's surface and its atmosphere. Greenhouse gases strongly absorb this radiation in the Earth's atmosphere, and radiate some back towards the surface, creating the greenhouse effect. See radiation, greenhouse effect, enhanced greenhouse effect, global warming.

(IR) electromagnetic radiation with wavelength longer than visible light but shorter than that of microwaves . Infrared radiation is produced by hot objects; absorption of infrared radiation causes chemical bonds to vibrate.