Overland/Dungeon Term Definitions

AddsSmaller, non-boss enemies.
AggroTo "have aggro" is to be targeted by enemies; to "pull aggro" is to get the attention (and therefore be attacked) by enemies.
AoEArea of Effect, usually a damaging attack. Enemy AoEs are by default a red area on the ground.
ChestsTreasure chests can be looted by only one person in non-instanced areas (in the open, public dungeons, delves) and by the whole group in instanced areas (dungeons, trials).
CrownThe group "lead," indicated by a crown icon. Whoever has the crown is the only person who can set dungeon difficulty, put group rally points on the map, invite people to the group, or disband the group. "Stack on Crown" is a common command for the group to stand in the same place as the character with the crown. In overland events, group members should stay with the person with crown unless directed otherwise. Never run ahead of the crown.
DelveA small, non-instanced area with enemies and 1-3 bosses. Most delves have one boss except in Cyrodiil, where most delves have 2-3. A "Group Delve" in Craglorn is similar to a delve but has a "+" by the delve symbol on the map and is instanced and restricted to four players.
Don't Stand in Stupid"Stupid" is the enemy AoE, by default a red area on the ground. Move out of these to avoid damage. This is not an insult directed at a person.
DOTDamage Over Time, any damaging effect that continues to damage an enemy for a period.
DPSDamage Per Second. DPS can either refer to literal DPS, the average amount of damage a character can output over a sustained period, or the DPS role, which is a character primarily devoted to dealing damage (as opposed to healing or tanking).
FacetankingIgnoring a mechanic and taking the damage instead. The opposite of "Don't Stand in Stupid."
FocusThe primary target for DPS
Group DelveA Craglorn delve that is instanced and restricted to four players. These are indicated on the map by the delve symbol (torch) with a "+" symbol.
Heavy CrateThe Coldharbour version of a heavy sack.
Heavy SackA lootable container. In non-instanced areas, these can only be looted by one person. In instanced areas like dungeons and trials, they can be looted by every member of the group.
HOTHeal Over Time, any healing effect that continues over a period of seconds.
Instance (noun)Your version of the area. When there are a large number of players in an area, they will be split into two or more "instances" and will not see each other or be able to interact. If you are partied with someone in a different instance, you will see their health bar but not them. To join their instance, travel to them.
Instanced (adjective)Only the people grouped will experience the same "instance" of the area. No random, ungrouped players will be encountered. Trials and group dungeons are instanced, as are "group delves" in Craglorn. In non-instanced areas, heavy sacks and treasure chests can only be looted by one person. In instanced areas, heavy sacks and treasure chests can be looted by the entire group. They will disappear once all members have looted them.
KiteTo lead an enemy or attack by running ahead of the attack, forcing the enemy to chase.
Leroy JenkinsTo run into a fight before the group is ready. A bad thing. See here for the original meme.
Leroy TankinsThe battle cry of the enthusiastic tank.
OverlandNot instanced, ie, not a group dungeon or trial.
ProcAn item ability that is triggered by something else. For example, a set that summons a Daedroth when you light or heavy attack.
PullTo pull (verb) is to aggro or start combat with enemies. A pull (noun) is a group of adds that are fought together.
Quest LockedAnything that requires the completion of a quest to access. For example, a wayshrine in the Rift, daily dragon hunting quests in Southern Elsweyr.
RandoAn unaffiliated player, random person.
ShiniesLootables, such as harvest nodes, heavy sacks, and chests.
SnackA heavy sack.
Stackstand as close together as possible.