Vent
Vent has 2 meanings
Ventrilo
Gamers use Vent as shorthand for Ventrilo, a voice and text chat program. Often, gamers use Vent to chat with others as they play multiplayer online games.
Ventrilo allows gamers to host their own chat servers, which they and other players can connect to. Notably, Ventrilo does not require a lot of system resources, and thus does not slow down players' computers when they play resource-intensive online games. For this reason, some gamers still use Ventrilo, even though several "better" options exist.
Example
I switched from Vent to Discord this year and won't go back
Eh, I like Vent's simplicity. And the sound quality's always ace
How well do you know your texting slang?
To vent means to express your displeasure about something bad that happened to you. This slang term is derived from the verb vent's actual meaning, which is to allow air (or another substance) out of a confined space. (In the slang version, you're letting anger out of the confined space that is your body.)
Typically, people vent to their BFF, SO, or someone else they're close with, who is willing to commiserate with their sob story. People may also vent in private or, in extreme situations, to any unlucky soul who happens to be around.
Other meanings of vent
If you're discussing the video game Among Us, vent means something else entirely. In Among Us, Imposters and Engineers can use a map's ventilation system to quickly move from place to place. This ability is referred to as vent or venting.