L'etranger

A novella written in 1942 by Albert Camus, also a pole-arm weapon in Metal Gear Rising: Revengeance, also also a primary that replaces the revolver for the Spy class in Team Fortress 2 (Former two are probably named after the book). Means "The stranger" in French. Apparently nobody knows how to pronounce it.

Hey dude how do you pronounce L'etranger?
I think it's Lee-train-jer

Oh they fuckin'

Used as an alternate, more colloquial, version of "I ship it". Literally means "Character x and y are going to have sex together".

Person 1: Person 2, I trust you with all my heart.
Person 2: I can say the same for you
Bystander: Oh they fuckin'!

Matthew

A tall blonde Gyrosexual apparently

Matthew! Stop drinking the green liquid hand wash in a sexual way!

imposter

An alternate spelling of impostor that has been popularised because of Among Us because the -er sound makes more sense than an -or sound.

Red is obviously the imposter
You mean impostor right?