but what does it MEAN?

[Fame]

it's a red cultural thing, it's aproval or support in meaning. Nothing specific and no abbreviation. Pras means pras.

Someone you like gets killed and the server broadcasts the kill in what we call "yellow text": Pras

Someone says something you agree with: pras


It can also be used as a bit of a tease.

Someone says something so stupid you almost feel sorry for them: pras

Its most common use is both approval and taunting of a yellow text kill. Most often when a bigger name on the server goes down. It doesn't really matter who gets the kill, it's about who got killed.