This document provides definitions for common abbreviations including RADAR (Radio Detection and Ranging), MASER (Microwave Amplification by Stimulated Emission of Radiation), PVC (Polyvinyl Chloride), DDT (Dichloro Diphenyl Trichloroethane), TNT (Tri Nitro Toulene), AWACS (Airborne Warning and Control System), CFC (Chloro Fluoro Carbon), AIDS (Acquired Immune Deficiency Syndrome), and BCG (Bacillus Calmette-Guerin).