CIM - Common Information Model describes how information is organized relating to computer systems, mangement, networking, etc. to allow vendors to count on a common API for accessing this information. See here for way more info.
COS - Console Operating System provides users and software agents access to system resources for configuration, backup, management, etc. The ESX 3.0 COS is based on Redhat EL 3.
NPIV - N_Port Id Virtualization which allows N_Port Ids to share physical ports. Implemented in VMware ESX 3.5 to provide a virtual HBA that maps to a physical NPIV capable hba. See bottom of p. 3 here
TLA - Three Letter Acronyms