Terahertz Radiation Definition

noun
Electromagnetic radiation with waves of frequencies ranging from 0.3 × 1012 to 3 × 1012 hertz and of wavelengths ranging from 0.1 to 1 millimeter of potential use in detection, imaging, and communications technologies.
American Heritage

(engineering) Electromagnetic waves with frequencies around one terahertz.

Wiktionary
(engineering) Especially electromagnetic waves in the range 0.1-30 THz (subranges there of, see T-rays or T-waves).
Wiktionary
Submillimeter wave radiation.
Wiktionary