Electronic Switching System 
Environmental Stress Screening 
Exploitation Support System 
Extended Service Set 
Enviromental Software & Services 
Earth and Space Sciences 
Energy Storage Subsystem 
Engineering Support System 
Enterprise Storage Server 
Earth System Science 
Electronic Security System 
Electronic Switching Systems 
Environmental Stress Screen 
Essential 
European Spallation Source 
Economics Statistics System 
Electronic Security Squadron 
Electronic Support Section 
Electronics Switching System 
ELINT Support System 
Embedded Security System 
Emergency Separation System 
Emplaced Scientific Station 
Employee Self Service 
Employment Support Services 
empty sella syndrome 
endoscopic sinus surgery 
Engineering Support Subsystem 
Enterprise Storage Servers 
Enterprise Systems Support