You might think you can walk the walk, but can you talk the talk?
I mean, maybe, you might've just come here to see what I considered 'important slang' but I'll keep going anyway.
Being able to communicate effectively and process information is a core tenet of Trouble in Terrorist Town, as with any social deduction game.
RDM, or RDMing, means to randomly kill someone as an innocent or non-traitor role; killing people for no reason can spoil the fun for them.
The term most often used to describe a dead body in the gamemode.
A dead body that hasn't been interacted with. Innocent players will want to interact with bodies to understand who is, and isn't, alive; typically only Traitors will leave bodies unidentified.
Saying someone is 'proven' or 'clear' means that they're proven innocent, or cleared of suspicion. Take this with a grain of salt and use your intuition, however.
When a player dies in the game and shares information to people still playing, this is called 'ghosting' and is considered poor play. On average, when dying, players will mute their microphones or stop talking so that they can't outright say how they were killed, who by, or so on. Not getting a response when you ask to speak to someone is a cool moment in the gameplay, too, so it's nice not to cheapen it.
'Claiming a role' means telling people what role you want them to believe you are; this is an attempt to avoid suspicion or clear yourself of it. Claiming a role like Jester would make people less likely to kill you, as it would make them lose, but there are ways to test your role; including that Jesters cannot do damage and they can just ask you to use your Crowbar on someone.
Conversely, 'counter-claiming' is when someone claims to have the same role, typically when only one of that role can exist, to discredit you and try and come off as clear themselves. These terms are typically used in Mafia, rather than TTT, but you can still see them now and again.
Shortform version of 'throwing [someone] under the bus', used to express when a Traitor is accusing their, often less-effective, partner of being a Traitor so that they might appear clear to the Innocent team. Not to be confused with 'bussy'.
Said, or typed, followed by a username (such as, 'kos Thighs'); this is used to communicate that someone is proven guilty (often illegitimately).
Some maps, not all, have red-outlined mouse cursor buttons in certain areas that only Traitors can see. When the Traitors press E on them, they will have a beneficial impact on the game, such as opening doors to 'T-Rooms'.
Traitor Rooms are areas that are accessible to the traitor team through hidden buttons or checks the map maker puts in to see if they are a traitor.
These often feature portals to other areas of the map, to travel faster, buttons for traps to kill innocents nearby that are seen through one-way windows, or serve as places to hide.
Some people prefer to say 'T-Tester' as a shorthand for 'Traitor Tester', a device that can discern if a player is a traitor or not. Most often, these put the player in a sealed box after another player presses a button, then it will show a green light for an Innocent role, or a red light for a Traitor role.
Lamentably, this is worth including. Calling someone 'sus' means you're suggesting they are 'suspicious', or saying 'I'm sus of [name].' does the same.
Translates to, 'If I die, this person likely did it because I can see them and I'm announcing that!'
Interacting with a dead body allows you to press a button that reads 'CALL DETECTIVE', this button puts a marker on the Detective's screen that will lead them to the body.
With their unique equipment, such as the DNA Scanner, the Detective will be able to make better use of the body than the average Innocent player, meaning that when someone asks you to 'Call the Detective', they're asking you to press that button.
Bear in mind, some players will ask you to do so to trap you, or kill you easier, a person's killer will typically know where a body is. Ask why they can't do it, if you are suspicious of them.
The Barnacle is an enemy from Half-Life 2 that is immobile, clings to ceilings, and must be shot to free yourself from the grasp it has on you if it catches you. In TTT, it is a Traitor shop item that can be placed on a ceiling where it will wait, invisible, to catch players that walk under it.
Unlike Half-Life 2, however, you cannot free yourself and must rely on other players to do so; often, this often results in a Traitor getting caught in their own Barnacle and dying in quite a humiliating way.
Asking someone if they were 'in the shop' or a 'menu' is a polite/joking way of accusing them of buying items as a traitor if they're standing still a lot.
People that think they're clever but that are actually very annoying will ask this to a suspected Traitor in an attempt to catch them out.
Innocents will have the role on their screen at all times, meaning all the Traitor really needs to do is either claim that they're a non-standard role, or refuse to do so.
This line of inquiry also adversely affects players that may find spelling, or processing relevant information, difficult and is too 'metagaming' a strategy for me to feel like I want to promote.
If you disagree with me, I don't care.