from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A unit of explosive force equal to that of one billion (109) tons of TNT.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A measure of the strength of an explosion or a bomb based on how many billion tons of TNT would be needed to produce the same energy.
metric prefix giga- + ton (Wiktionary)