RDM – Random Deathmatch
VDM – Vehicle Deathmatch
OOC – Out of character
IC – In Character
Perma/Permadeath – Permanent death of a character
FRP – Fate RP/Roleplay
Value Life – Your life is important, take care of it as if you only have one
Meta Gaming – Taking information you have learned on other characters or OOC and applying it to in game circumstances with characters who would never have this information.
Power Gaming – Setting things up in a way in-game that allows characters to get ahead, usually by bending or abusing the rules.
NLR – New Life Rule. 
Combat Log – Quitting the server to avoid punishment or loss of items
Must Win – Needing to win every single shootout or RP scenario, usually without thinking about others. 
Mr. Clean/Default Danny – The base ped character when logging into the server for the first time. 
Fear RP – If your character is held at gunpoint, don’t run away, play out the scenario with your captors. Value your life.
Government Official – Server Admin

General In-Server Terms & Phrases

Spider – In-Character way to say that a player is glitching and needs to jump as their character to clear/fix it. 
The City – In-Character way to say “The Server”.
Voice Box – Your computer microphone
The Government – The people who run & manage the server/owners/admins/mods
Government E-mail – Discord DMs or channels
Headache – Player is experiencing an internet connection/server disruption
Take a Nap – Player needs to relog
My Eyes – The way in which a player saw something that is different from another player due to server lag or connection issues
Tsunami – Server restart
Cop Bait – Circling or harassing the cops for an extended period of time
LEO – Law Enforcement Officer

fivem specific Terms & Phrases

On a Flight – Player is coming into or leaving the server
SASP – San Andres State Police
BCSO – Blaine County Sheriffs Department
LSPD – Los Santos Police Department