from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. Electromagnetic waves with frequencies intermediate between, and sharing properties of both, short radio waves and long IR optical waves. This region is defined variously as between 0.1 - 10 THz, 0.3-3 THz or 0.3-30 THZ.
The letter T- from TeraHertz (THz). (Wiktionary)