Proc Proc is an acronym for a programmed random occurrence that refers to a weapon , item or ability activating with the " Chance on Hit " or " Chance on Use " effect ( an ability or a spell ) . History . Proc is a common term used primarily in game programming to refer to an event triggered under particular circumstances . For example , in WoW , a particular weapon ( that hits many times ) might have a 10 % chance on each hit to apply a special effect , such as poison damage . When WoW users talk about " how often this weapon procs " , they are talking about the likelihood of the special effect occurring . Proc was originally short for " spec _ proc " ( spec _ proc is short for " special process " ) which is a term used by the original programmer of Circle - MUD , Jeremy Elson . It might have been used by the original programmers of diku - MUD as well . Special processes in Circle - MUD are functions that can be assigned to objects , players , and locations in the world such that each time an event occurs , the special process function will be invoked . Special processes were used in Circle - MUD for a wide variety of purposes : Creating room events when a person typed a specific string of text , causing a weapon or piece of armor to perform a magical action , and even causing a mob to do something that it wouldn ' t normally do . Special processes were a way of creating unique experiences that could not be achieved by simply building the dungeon and populating it with monsters . Special processes breathed life into these worlds by introducing extra coding that enhanced the gamer ' s experience without changing the underlying structure or function of the code - base . If you ever played a MUD and were walking around in a dungeon and randomly saw the text " You feel as though you are being watched , " that was probably a special process . When developers and players were talking about these special processes they abbreviated the term to " proc " . Over time the noun also became a verb , " proced " ( " proc ' d " or " procced " ) , which meant that the special process was invoked and performed its action . Most often , players were concerned about their weapons and whether or not the weapon would perform its special attack ( a proc ) , and so proc must have started to take on a narrower meaning for MMORPG players who were somewhat more removed from the core combat engine and flat world of MUDs . In World of Warcraft . In " World of Warcraft " , players refer to items that have Chance on Use or Chance on Hit effects as having a proc . Most of the time these items are weapons but they can also be armor , rings , trinkets , and even spell effects . How these items trigger their proc ( s ) depends upon what kind of an item it is . " Programmed Random OCcurence " is another definition , thought to be correct by many WoW users , though whether or not it is indeed correct is debatable . Guaranteed effects from critical hits ( like " after a critical strike your attack speed is increased by 30 % for 15 sec " ) are called proc too ( the effect is automatic , but the critical hit is rare . Several classes have abilities that will unpredictably activate - for example , a druid ' s Omen of Clarity or a death knight ' s Killing Machine . The event of these abilities activating is also called a proc . Weapons . For weapons that have a proc , they usually have a Chance on Hit to either aid the wielder , harm his target ( s ) or both . Procs can also be added to weapons by enchanting them with certain enchants . The proc - rate of a weapon is the frequency with which the weapon triggers its proc . This varies depending on the nature of the weapon and how it is wielded . Certain epic weapons have a very high chance of proc ' ing ( 30 + % ) , but most players report that wielding one - handed weapons in your off - hand reduces the proc - rate by 50 % . PPM . It has been proven however that enchantment procs are based on something called Procs per Minute ( PpM , PPM , or ppm ) . This in essence makes slower weapons , especially on a class like a rogue with instant attacks boosting their attacks per minute like crazy , actually proc more than faster weapons . The PPM system works as follows : The actual chance each hit with a weapon procs the effect is PPM * weapon speed / 60 . Dual wielders should note that all instants ( including the extra attack granted by Sword Specialization talent from Warriors & Rogues ) always happen with the main hand weapon , severely increasing the number of hits per minute with that weapon . ( This also explains as to why people find OH weapons proc much less ; they just don ' t hit as much ) Armor , Rings , and Trinkets . Worn items such as these can either trigger their proc when the wearer is hit in combat , when the wearer casts a spell — offensively or defensively , when the wearer uses the item , or when the wearer hits his opponent with a melee attack . That would tend to make the first proc more valuable to players who get hit quite often , in other words PVPers and warriors , the second and third proc useful to anyone , and the fourth proc most useful to melee combatants like rogues . Spell Effects . Some spell effects can also grant players a proc . Examples : The Druid spell Thorns grants the player a proc that damages his attackers when they strike him . The Warlock ' s Imp spell Fire Shield is similar to Thorns . The Shaman spell Windfury Weapon causes each attack to have a chance of permitting a free attack with a bonus to their attack power . Both the Paladin seals Seal of Command and Seal of Righteousness have a chance on hit to cause holy damage ( though in " very " different ways ) .