This is a list of common IT abbreviations. It will be completed in the course of time.

APTAdvanced Persistent Threat
COTSCommercial Off-The-Shelf (aka Shrink-Wrapped Software)
CSRCertificate Signing Request
CVECommon Vulnerabilities and Exposures
CVSSCommon Vulnerabilities Scoring System
DASTDynamic Application Security Testing
DMVPNDynamic Multipoint Virtual Private Network
EISAEnterprise Information Security Architecture
EPPEndpoint Protection
GREGeneric Routing Encapsulation
IAMIdentity & Access Management
IDSIntrusion Detection System
IOCIndicator of compromise
IPSIntrusion Prevention System
LWFDilbert rulez!
MPLSMultiprotocol Label Switching
NGFWNext Generation Firewall
NHRPNext Hop Resolution Protocol
NVDNational Vulnerability Database
QoSQuality of Service
SASTStatic Application Security Testing
SDDCSoftware-defined Data Center
SICSecure Internal Communications (Secure communication protocol between Check Point components)
SKUStock Keeping Unit
VRRPVirtual Router Redundancy Protocol
VSXCheck Point's Virtual System Extension to virtualize firewall gateways within physical hardware.

To be continued…