Open PvP refers to a type of online game were any play can attack any other player with out restrictions. The players can attack anyone at any time.

"Open" refers to that availability of it. and "PvP" refers to Player versus Player.
"Because the game was Open PvP, I had to be careful and watchful for other players that may attack me in any place at any time."
by Harvard Dictionary March 17, 2014
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RPG refers to Role Playing Game; See RPG.

Open PvP is a term used in RPGs to describe the freedom of a RPGs world. PvP refers to Play vers Player. Open refers to any play can compete with another player in any given way.

In the context of a RPG, they would be competing with another player for a reason that fits their characters role. If they attack everyone, they could be considered a murderer. In that role they could expect the game to hunt them and a life of hiding with other outlaws.
"The game was an Open PvP RPG. I was Role Playing a Murderer and would try to kill other players. The games NPC Police were out to get me so I had to hide often."
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PVP that takes place in an Open World. Many instances of PVP take place inside instances, zones created for the PVP in which set numbers of players fight in their own personal map until a victory condition is set and that copy of the map goes away. By contrast the Open World is a non-unique setting that you and other players can freely move around, so Open World PvP contains a lot of unpredictability and often starts with randomly encountering hostile players.
I'm tired of these arena matches, let's go to hostile territory and do some Open World PVP.
by Andius June 6, 2017
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