A stunlock (also called stunlocking) is the act of using multiple stuns and immobilizing effects in succession to prevent an enemy from fighting back or escaping. As a result, a stunlock sacrifices a large amount of DPS in exchange for keeping the opponent "locked down". Although typically and most easily accomplished by a rogue, it can also be achieved to lesser degress by warriors, paladins and druids. Some refer to this ability as a full kill of an enemy player in PvP without allowing them to react, whereas others consider a small sequence of stuns a stunlock.
Talents and Abilities affecting Stunlock
Some classes' Faction Insignias free the user from stuns. Additionally, there are many talents, such as 
[Nerves of Steel] for Rogue, 
[Iron Will] for Warriors, and Unbreakable Will for Priests, that grant stun resistance. Finally, orcs have a racial called 
[Hardiness] that gives them a 15% chance to resist stuns. A paladin's 
[Divine Shield] and 
[Blessing of Protection] instantly breaks him/her from all stuns.
How to Perform Stunlock (Rogue)
A rogue can perform a stunlock in a variety of ways, some of which include 
[Thistle Tea] or 
[Renataki's Charm of Trickery], means by which to gain extra energy. A rogue's effectiveness at performing a stunlock is dependent on his or her build. For example, a full combat build or a 
[Seal Fate] build without 
[Vigor] would be least effective for stunlocking while a 
[Cold Blood] and 
[Hemorrhage] build would be most effective.
Here are some stunlock strategies:
- For a Hemorrhage build:
Cheap Shot -> Hemorrhage x2 -> Kidney Shot -> Hemorrhage x1 -> Gouge. Restealth using Vanish. Repeat.
- For a Hemorrhage build:
Cheap Shot -> Hemorrhage x1 -> Gouge -> Kidney Shot.
- For a
[Cold Blood]/ [Preparation]/ [Hemorrhage] build:
Cheap Shot -> Hemorrhage -> Gouge -> Kidney Shot -> Hemorrhage x2 -> Blind -> Slice and Dice -> Restealth. Once blind is about to fade: Cheap Shot -> Hemorrhage -> Gouge -> Kidney Shot -> Hemorrhage x2-> Eviscerate.
- For a [Seal Fate]/ [Vigor] build using daggers:
Cheap Shot -> Sinister Strike -> Gouge -> Kidney Shot -> Backstab -> Blind -> Restealth. Once blind is about to fade: Cheap Shot -> Backstab -> Kidney Shot -> Backstab.
Note: If you possess 5 pieces of Nightslayer Armor you can complete the second half using:
Cheap Shot -> Backstab -> Cold Blood -> Eviscerate.
- For an [Adrenaline Rush] build:
Cheap Shot -> Adrenaline Rush -> Sinister Strike -> Gouge -> Kidney Shot -> Sinister Strike x3 -> Blind -> Restealth. One blind is about to fade: Cheap Shot -> (Wait for Energy) -> Kidney Shot -> Sinister Strike x3.
It should be noted that, for the most part, stunlocks are confined to the realm of 1v1 PvP and dueling. Any interference by other players during a stunlock may prevent the rogue from executing his or her next stun, which in turn allows the target a chance to break out of stunlock. Furthermore, the stunlocks listed beforehand require precise timing to avoid diminished returns. Each ensuing stun must be timed to land just as the previous stun is about to fade.
Applicable Addons
Stunwatch and CCwatch, both available from Curse Gaming, track the duration of your stuns allowing for better timing. Natur's EnemyCastBar (also hosted at Curse Gaming) does the same tracking of diminishing returns, allowing the player to time the second use of his abilities in a way that does not reduce their effectiveness.