Acronyms

ADB - Android Debugger, a utility to run on a PC to allow connection to and control of an Android device

AKU - Adaptation Kit Update: they usually patch up existing bugs and enable several new features. Each newly released AKU pack retains fixes found in previous versions of AKU

CSC - File with Carrier Customizations

CID lock (aka vendor lock) - put on your device by the manufacturer to prevent installation of a ROM not released by them

CM - CyanogenMod, an alternate firmware for your phone, with the stuff your carrier left out, and more

CWM - ClockWorkRecoveryMod, an alternate recovery mode for your phone, with the stuff your carrier left out, and more

ESN - Electronic Serial Number unique to your phone (usually in hexadecimal or decimal)

FC - Force Close, AKA application crashed

gapps - Google Applications, like GMail, Calendar, Maps, G+, etc

GB - Ginger Bread, AKA Android OS 3

ICS - Ice Cream Sandwich, AKA Android OS 4

IPL - Initial Program Loader: Its the bootloader for PPC. It boots up SPL.

MMS - Multimedia Messaging Service (text messaging with pictures)

MSL - Master Security Lock (the six digit code needed to program your phone)

OCUV - Over Clock/Under Volt the CPU to save power and increase speed

OTA - Over-the-Air (usually used as "OTA update" for firmware updates that can be installed directly via 3G/4G/Wi-Fi without the need of an PC)

PRI - Product Release Instructions (default settings your phone ships with)

PRL - Preferred Roaming List (tells your cellphone whose towers to use when roaming)

RIL - Radio Interface Layer

ROM - Read-only memory. Can also refer to a custom ROM firmware file

RUU - ROM Upgrade Utility: Its the s/w used on your PC to do a ROM upgrade for your device

SMS - Short Messaging Service (text messaging)

SPL - Secondary Program Loader: Loads the actual OS.

WiMAX - Worldwide Interoperability for Microwave Access.

WWE Edition - World Wide English Edition

UC - User Customization

XIP - Execute-in-Place

More in the FAQ Section.