[Verizon Samsung Galaxy S 4] decaturbob:
I copied this from andriodforum post and give full credit to Nomorefear,

ADB- Android Developers Bridge: The program used to talk to your phone and give it commands (USE IT ONLY IF YOU FEEL COMFORTABLE LEARNING)

Root/Rooting- Getting the administrative control i.e, "hacking", "jailbreak", etc, etc...... Root is also defined as the base folder of your SD card. If you are told to place a file into root then this is what is meant. REMEMBER-root/rooting-admin control OR base folder on SD card. Please re read instructions you find in the forums throughly so that you may be able to save yourself some time and heartache.

Superuser- program which gives authority for another program to have Root access. Program examples are "setcpu", "terminal emulator", "auto killer memory optimizer"

Recovery- a useful tool that allows root users to flash roms, reinstall backups, and do many other fantastic things to help keep your phone from becoming a brick.

Flash/flashing- the action of "installing" a file that isnt normally installed by conventional means i.e. flashing a rom, flashing a radio, flashing a kernel, etc etc. '/!\ WARNING: flash at your own risk and make sure you have over fifty percent battery and do not interrupt the flashing procedure. YOU HAVE BEEN WARNED!!!!!'

Brick- making a device useless so that it is rendered a mass of uselessness i.e. PWNED, paperwieght, borked

Terminal Emulator- a program which simulates ADB and basically is a way to communicate with the phone and provide a command language that is for upper eschelon (1337) users to helm.

Nand/nandroid backup- In your recovery terminal there is an option to make a "Nand backup". This is a restore point or in gaming terms a save point. As most of us gamers know, if you save before you go further in the game and you make a poor choice then you can reset and go back to where you started. This is the same thing but for your phone

Kernel Easiest way to put it: it is the thing that manages your system resources. This puppy can help make your phone run better and also overclock it.

Overclocking Dont worry I wasnt gonna leave this term out. This is written for newbs so lets just say this is the term for making your phone run faster. IMPORTANT NOTE!!! Overclocking your phone too far can make it seize up or go into bootloops if done incorrectly! It can also make your phone run hot. BEWARE!!!!

PRL Preferred Roaming List: This is just an updated list of what cellphone towers have been added to the system. This means better coverage when updated" - Nomorefear

Here are some other definitions not covered by Nomorefear. For the following, I give credit to Wiki CMS Groupware (makers, I mean "developers" of Titanium Backup). I've also modified their stuff a bit. Link at end of post.

More DEFINITIONS

system app - A system app is an application that resides in /system/app/ and thus is technically a part of your ROM

user app - is an application that resides either on the /data partition of your phone's internal memory or on your SD card

system data - In the vast majority of cases, system data is simply the data that belongs to system apps or services.

root - is the UNIX system administrator (UNIX is an operating system [OS] just as MicroSoft "Windows" is an OS)

NAND locked (or "S-ON") device - is a device where the ROM (usually mounted at /system) is write-protected in hardware and thus cannot be modified, even if you have root privileges. Sometimes you get the illusion that you can write to /system, but in any case all changes will disappear after a reboot. This is why these devices often have "temp root" instead of permanent root". In order to get permanent root access, you need to make your device "NAND unlocked" (or "S-OFF") first. In other words, you need to "unlock the bootloader".

shell - simply is a "command line" to type commands on your Android phone. If you're comfortable with typing on the phone then you can just use the ConnectBot (free) app or the Better Terminal (paid) app. If you want (or need) to type commands from a computer, just install the Android SDK, then enable "USB debugging" on your phone and finally, connect your phone through USB and type "adb shell" on your computer.

Here is another definition from kejlyCZ (link at end).

"ROM - is abbreviation for Read Only Memory. In this case, it's the part of the phone software, which is provided by manufacturer (operating system, basic built-in programs) and it's protected from deleting by user. It's the same like when you install Windows, the clean installation with no user data and user installed programs. In Android, ROM means the Android operating system. It can be the official ROM (updated by manufacturer) or unofficial ROM (AKA "Custom ROM) ('brewed' by community,.....

And FINALLY (unless I edit later):

Boot Loop or Boot Looping - your phone keeps rebooting endlessly until you turn it off or throw it against the wall, there are a number of ways to get out of boot loop