- Party - A player can invite other players from their friend list to form a team before joining a match. If the amount of participants does not reach the maximum size of the selected match mode (3 or 5), they will be placed with solo players to fill the vacancy.
- Panth - Pantheon
- Path or Pathing The route that will be taken towards a destination.
- PD - Phantom Dancer
- Pentakill - Slaying five enemy champions within a certain length of time.
- Peel - Keeping enemy champions off your carries by "peeling" the enemies off them with your body or abilities.
- Pet - A non-champion, non-minion ally that may or may not be controllable that is generated by a champion's ability and fights for him on its own.
- Ping - To alt/G+left-click on the mini map causing a "ping" noise and a mark on the map that your entire team can see.
The latency of player's internet connection to the game server, measured in "ms" (millisecond, 1 ms=0.001 second).
- Poke - A form of harass which uses long ranged attacks to cause small to moderate damage in order to weaken an enemy, while keeping a safe position.
- Position or Positioning A champion's location during a fight. Good positioning is determined by the player knowing the optimal location their champion should be at.
- Pot - Potion(s), usually Health Potion.
- Premade - Multiple players, who know each other, forming a team together before entering the champion selection phase.
- Pro - An act of calling someone that is very talented when playing.
- Proc - Programmed Random Occurrence
- Purple - Purple Team: The group of players that start out at the upper-right side of Summoner's Rift, or right side of Twisted Treeline and Crystal Scar.
- Push - To continue advancing forward in a lane, clearing it of minions and towers.
- LDR (Lord Dominik's Regards)
The capture points of quarry or boneyard in Dominion mode.
[li]SS Enemy champion missing, shortened form of "miss". "SS" (along with "miss") is more common than "MIA" in the European server.
The X and Y categories have odd line wrapping.
Also missing "ADC" and "Marksman". "AD" can also be an abbreviation for "ADC".
Missing the words 'Peel' and 'Spell Vamp'
Exp - Experience Points
Grag - Gragas
Heca - Hecarim
HPS - Healing Per Second
Kha / Khaz - Kha'Zix
There's "Kat" but people also use "Kata" - Katarina
Malph - Malphite
Malz - Malzahar
Mord - Mordekaiser
Mumu - Amumu
Mao - Maokai
MPS - Mana Per Second
Naut - Nautilus
Ori - Orianna
Panth - Pantheon
QQ - Can also mean "Queue"
Shyv - Shyvana
Seju - Sejuani
Trist - Tristana
Vik - Viktor
Vlad - Vladimir
Voli - Volibear
Vision Ward - A ward that allows you to see invisible units in a small area.
Wolves - The Wolves camp in jungle
Wraiths - The Wraith camp in jungle
WA - Warmog's Armor
XP - Experience Points
I think you're missing these ;)