1. A unit of weight equivalent to 1 billion tonnes
   "Annual carbon emissions are measured in gigatonne";
   - Gt
    
2. [Brit] A measure of the strength of an explosion (or bomb), equivalent to a billion tons of TNT (to produce the same energy)
   "The impact of the asteroid was estimated to be several gigatonnes";
   - gigaton

Derived forms: gigatonnes

Type of: metric weight unit, weight unit

Encyclopedia: Gigatonne