Abbreviations
AA - auto attack, the right-click your champion does to opponenets
ADC - attack damage carry, a champion in the bottom lane, used generally for any bot laner although technically different to a mage / ability power carry (APC)
AoE - area of effect, where an ability can have an impact
AP - ability power, the strength of a champion's abilities
CC - crowd control, managing the waves of minions and champions in a teamfight
CD - cooldown, when you use an ability, time must pass before you can use it again
CDR - cooldown reduction, allowing you to reduce the time between using the same ability again
CS - creep score (minions killed)
DPS - damage per second, there is also the separate DoT for damage over time
ER - Essence Reaver, an item that provides +70 attack damage, +25% critical strike chance and +20% cooldown reduction
GG - good game, said at the end of matches
IAS - increased attack speed
IE - Infinity Edge, an item that grants +80 attack damage+25% critical strike chance and an increase in critical strike damage by 25%
KS - kill steal, overused phrase for when a champion is set to get the kill but another champion 'takes' it
MR - magic resist, the equivalent of armor but for magical attacks
MS - movement speed (not to be confused with ms in the top right corner)
TP - Teleport, a summoner spell you can bind to D or F by default that allows you to send your champion to an allied structure or champion quickly
VGU - visual and gameplay update, another way of describing a rework with significant changes
VO - voiceover, champions often deliver voice lines as they are played
Terms
Ace - when a whole team of five champions is killed by the opposing team
Ban - in modes with a draft, each team member can ban a champion that prevents it from being picked by allies or enemies
Baron - Baron Nashor is a huge and powerful monster in the jungle that first spawns at 20 minutes and gives the Hand of Baron buff to the team that kills it
Baron Pit - the area in which Baron Nashor and the Rift Herald spawn
Blue Buff - the Crest of Insight buff is given to the champion that kills the large Blue Sentinel in jungle
Brush - the tall grass in which champions and wards turn invisible
Camp - where monsters spawn, these are set areas in every game so are known before the start
Chickens - the Raptors are the bird-like creatures that spawn in the jungle
Counter - champions that are a strong matchup against their opponenet, counter picks often give you a better chance of winning through kit alone
Damage - three types of damage can be dealt - physical damage, magic damage and true damage - with the latter ignoring armor and resistance items/stats
Dive - going under a turret to engage with and kill a champion knowing you will take significant damage
Dragon - in the bottom right of Summoner's Rift, different elemental drakes spawn here that provide different buffs when killed
Elder Dragon - a strong monster that spawns 35 minutes into the game and when killed, grants the Aspect of the Dragon buff
Engage - the act of entering into a fight with disengaging being the opposite
Farm - gaining gold and exp from minions and monsters
Fed - a champion that earns many kills and levels up above opponents is 'fed'. Dying multiple times to another champion, this can be described as 'feeding'
Focus - usually followed by a champion name, this means the team should seek to eliminate that champion to give a higher chance of winning a fight
Fog of War - the dark areas of the map over which players do not have vision
Gank - a surprise attack that seeks to ambush and eliminate an enemy champion, often the junglers who have the most freedom to gank all three lanes
Herald - the Rift Herald is a large and strong monster that spawns once a game at 9:50 and drops the Eye of the Herald when killed
Kit - the set passive and abilities a champion possesses
Kite - staying out of range of enemies while attacking them and keeping them in place through slows, stuns or other CC
Last hit - the last hit is the killing blow to enemy champions, minions or mobs. This determines who receives gold or buffs in the case of the jungle monsters
Mana - the resource many champions have that allows them to use abilities that cost a portion of it to cast
Minions - the small mobs that walk down each of the lanes
Monsters - also referred to as 'neutrals' or 'mobs', these are the enemies that appear in the jungle such as the raptors and wolves
Peel - a means of enabling an ADC, peeling is preventing your carry from taking damage using CC
Penta - similar to an 'ace' when all enemies are wiped out, a penta is when one champion kills the five enemy champions personally
Pick - draft mode allows you to select, or pick, a champion
Poke - small damage to reduce enemy HP without seeking a kill
Pre - short for 'premade', used in lobbies by players to state they are queued with others in the lobby
Proc - short for Programmed Random Occurence, this term is borrowed from World of Warcraft to mean an ability/item that has an extra effect that can be activated
Push - leaving your lane or jungle to make progress in a lane as a team together to bring down a tower
Red Buff - the Crest of Cinders buff is given to the champion that kills the large Red Brambleback in jungle
Roam - not sticking to one area/lane on the map
Rocks - the Krugs are the rock-like monsters in the jungle that split into smaller versions of themselves when first killed
Root - similar to a stun, this debuff stops champions moving and roots them to the spot
Runes - special customisation that can tweak how a champion plays such as providing shields when hit or earning extra gold, this is explained in detail below in a YouTube video by Snow Fox
Silence - this debuff prevents a champion from activating their abilities
Smite - a summoner spell all junglers should have, this enables high damage to neutrals and bosses in the jungle
Smurf - someone who is using a low level or low rank account while their main account is of higher level and rank
Split Push - this involves the team pushing a lane while a teammate tries to make progress elsewhere while the opponent is distracted
Squishy - a champion that is easy to kill due to low HP on their side or high damage on the other side
Tank - strong durable champions who are capable of taking significant amounts of damage
Tower / Turret - the tall structures to attack and defend in each lane
Trade - an enemy champion kills you or another ally and is then killed
Ward - a unit that can be placed to grant vision in an area and come in multiple forms
Wave - the crowd of minions is commonly referred to as a wave
Ult - R for all champions is an ultimate, a special ability that allows for a powerful attack, buffs, transformations or other significant changes
Zoning - keeping a champion out of range for their attacks to land