Great thread! May I come with some (hopefully) constructive criticism?
It seems like certain terms are referenced more than once. I saw "Spinblocker" listed twice (both under Roles). "Auto Weather" is listed both under Common Abbreviations and under Other. "BST" is both listed under Roles and Abbreviations.
And frankly, most of the entries under "playstyles" could go in the abbreviations tab. "Ferro", "Lop", "Garde", "MegaMan" and such are clearly abbreviations and not play styles, at least the entries don't give the impression that the terms refer to more than the Pokémon themselves.
Back in the days (it might not be as relevant any more) there was a bit of confusion around the term "SD". In addition to meaning Swords Dance, it can also mean Sunny Day or Selfdestruct (And Smack Down, I guess). Should there be a sentence to clarify, perhaps? Neither of the two latter are much used any more, so I guess Swords Dance "won" that competition. Interestingly enough, it seems like Gen III Shiftry and Mew can learn all three moves (Mew can even have all four, if exported from Gen. III).
I'd also like an entry on the terms "4Drag2Mag", "ChainChomp" and "TyraniBoah", which were popular a generation or two ago. However, I don't know the specifics of the term well enough to explain them myself. However, there a couple terms I think I can do:
Abbreviation
Term: GG - "Good Game"
Explanation 1: A customary way to thank your opponent for the battle.
Explanation 2: A way to signal that the outcome of the battle is practically determined, even though it technically isn't over. Usually used by the winning side.
Example 1: "What a jerk. He was screaming about hax the entire battle, and when I won he didn't even say GG".
Example 2: "His Gliscor allowed me to set up Gyarados to +6/+6, and it was all GG from there on"
Reference: Common usage on the forums and Pokémon Showdown.
Other OR Abbreviation
Term: 6-0'd
Explanation: A battle ends with all 6 Pokémon on one side fainted, but 0 Pokémon on the other side.
Example: "A battle against a Jirachi can easily end up with you 6-0'd without a chance to retaliate because of paraflinch"
Reference: Common usage on the forums.
Other
Term: +6/+6
Explanation: A Pokémon which has boosted two of its stats to the maximum level, typically Attack and Speed or Sp.Atk and Sp.Def.
Example: Repeated usage of Dragon Dance or Calm Mind
Reference: Common usage on the forums.
Abbreviation
Term: Scarf
Explanation: Choice Scarf. Not to be confused with Silk Scarf (occasionally used by Arceus) or the Pokémon Contest scarves.
Example: ScarfChomp, ScarfTar, Scarfed Pokémon.
Reference: Common usage on the forums.
And one I'm a little uncertain of, but it's used a lot around here...
Abbreviation
Term: OI
Explanation: Orange Islands, the non-competitive "general Pokémon talk" section of the Smogon Forums.
Example: "We don't discuss the Battle Maison in the OU forum. Try asking in the relevant thread in OI".
Reference: Commonly used on the Smogon Forums.