FFA (also f-fa and variants): Fail Fandom Anon, the anonmeme you've been looking at.

• Nonny, nonnie, anon = the people posting comments on meme
• AYRT = anon you replied to
• AIRT = anon I'm replying to
• A AIRT RT = anon [whom] the anon I'm replying to [earlier] replied to (usually the anon two comments up instead of one)
• AVRT = anon velociraptor replied to
• NAYRT = not the anon you replied to
• SA = same anon (when you're adding to or correcting something in a comment you just submitted)
• NA = new anon (not previously part of the discussion)
• DA = different anon (possibly new to the subthread, may already be contributing to the discussion in a different subthread)
• OP = original poster (person who started the thread)
• SubOP = subthread OP
• YADA = yet another different anon
• YANA = yet another new anon (when it doesn't mean You Are Not Alone)

• A/B/O = Alpha/Beta/Omega[verse] fic or characters. See Dogfuck Rapeworld (or the Fanlore page) for details.
• ASOIAF = see GoT
• AFFN, AFF.net, variants = AdultFanFiction.net
• AO3 = Archive of Our Own, fanfiction archive created/maintained by the OTW
• AOS =
  1. “Alternate Original Series” (Star Trek reboot movies).
  2. TV series Marvel's Agents of S.H.I.E.L.D.
  3. Age of Sail (Horatio Hornblower, Aubrey/Maturin, etc.)
• ATG = Any Two Guys, more rarely Any Two Girls. In reference to fic with generic characterization; the pairing could be “any two guys.” Used in "Guess the ATG" game threads (beloved of nonnies for the creative name-swapping possibilities).
• BEC = (look at that) Bitch Eating Crackers, referring to a grudge that makes the bearer annoyed by even the most innocuous actions of the target
• BFE = Bangs Fests Exchanges, one of meme's common threads
• BNF = Big Name Fan
• BL = boys' love
• BTS = a K-pop boy band, also known as Bangtan Boys
• BtVS = Buffy the Vampire Slayer
• CBT = on FFA, equally likely to be earnestly used in discussions about therapy options (Cognitive Behavioral Therapy) or in discussions about kink (Cock and Ball Torture).
• CEBLA = Chris Evans' Butthole Loving Anon
• CTSC = comment(ing) to see comments. No longer a thing since the move to Dreamwidth.
• DCU - DC Comics Cinematic Universe
• DD = “Details, details!” A call for evasive/coy nonnies to spill the beans about whatever.
• DW = Usually either Doctor Who or Dreamwidth; depends on context
• DFRW = Dog Fuck Rape World
• EFRW = Eldritchfuck Roseworld, a loose multiverse of Homestuck AUs.
• EFW = existential flame war, based on the LJ comm of the same name, which originated in the Usenet group alt.callahans. Enjoyed by some, reviled by others.
• FMA = Full Metal Alchemist
• FFN, FF.net, FF, variants = FanFiction.net
• FWA = Fog Warriors Anon, Dragon Age troll
• GoT = Game of Thrones, TV series based on George R.R. Martin's A Song of Ice and Fire (ASOIAF).
• GotG = Guardians of the Galaxy
• GSN = Grumpy Sutcliff Nonnies
• HIMYM = How I Met Your Mother
• HPMOR = “Harry Potter and the Methods of Rationality,” a smug longfic by “rationalist” cultist Eliezer Yudkowsky
• HTGAWM = How to Get Away with Murder
• ITT = in this thread
• JGY = Jin Guang Yao, a character in The Untamed. Sometimes pronounced “Jiggy” by Western fans.
• LJ = LiveJournal
• LJW = Lan Wangji, a character in The Untamed
• LL = “Link links!” (unless you're an spnanonhaven/FFA bimemer, in which case it stands for “Leonidaslion”)
• MCU = Marvel Cinematic Universe. Includes (at least) the Thor, Avengers, Iron Man, and Captain America movies, as well as the Agents of S.H.I.E.L.D. TV series in its continuity.
• MDZS = Mó Dào Zǔ Shī/Grandmasters of Demonic Cultivation
• MFVW/MFCW = Mantis Fuck Vore [or Consent] World, an FFA-originated offshoot of DFRW/A/B/O.
• MLP, MLP:FiM = My Little Pony: Friendship is Magic. Meme critter Pinkie Pie either hails from there or named herself after one of the characters.
• MNF = Medium Name Fan
• MSF = Migratory Slash Fan[dom]. Refers to fandoms transiently popular with certain, particularly big-name slash fans, often with white-cock juggernaut pairings.
• NFHA = Nathan Fillion Hating Anon
• NN = author Naomi Novik aka BNF Astolat, cofounder of OTW. Formerly, often referred to by her initials to avoid linking her wallet name to her fannish pseud; now that she has herself connected the two identities and also personally and publicly accepted a Hugo Award on behalf of AO3, there's no reason not to do so.
• NNF = No Name Fan. Very rarely also LNF, Little/Low Name Fan.
• OAA = Overly Aggressive Anon
• OEA = Overly Earnest Anon
• OLA = Overly Literal Anon
• OSA = Overly Sensitive Anon
• OMD = Original Male Dog
• OTW = Organization for Transformative Works
• OUAT = Once Upon a Time. TV show based on fairytales, on which step-grandparent/step-grandchild incest is not intergenerational and a major pairing.
• POI = Person of Interest. TV show/MSF starring Michael Emerson from Lost and Jim Caviezel a.k.a. Jesus Cavesus
• PWP = Porn Without Plot, also known as “Plot? What Plot?”
• RPF, RPS = Real-Person Fic, Real-Person Slash
• SJ, SJW = social justice, social justice warrior.
• SnK/AoT = Shingeki no Kyojin/Attack on Titan, popular manga/anime series
• STID, ST:ID = Not in fact a sexually transmitted ailment, but Star Trek: Into Darkness (the 2013 movie, second in the ST:AOS continuity)
• SVSSS = Scum Villain's Self-Saving System
• SW: TFA = Star Wars: The Force Awakens. Often just “TFA.”
• TGCF = Tian Guan Ci Fu/Heaven's Official Blessing
• TMA = The Magnus Archives, a horror podcast
• TSN = On FFA, usually refers to The Social Network (2010 slashbait film), more rarely to The Sentinel (1990s slashbait TV series)
• TW =
  1. Teen Wolf.
  2. Torchwood.
  3. Trigger warning. Depends on context.
• TYWAU = Things You Wouldn't Admit Unanon. One of the common threads on the meme, usually on the first page. Occasionally rendered as “TYWNAU.”
• WKX = Wen Ke Xing, a character in Word of Honor/Faraway Wanderers
• WS = He who shall not be named, for he is a notorious self-googler and will show up to act out on meme.
• WSA = Weird Scenario Anon. Just what it says on the tin.
• WSJ = On meme, normally Weekly Shounen Jump, a major manga magazine, rather than the Wall Street Journal.
• WTNV = Welcome to Night Vale, a podcast
• WTNVNA = Welcome to Night Vale Hating Anon, a long-time troll
• WWX = Wei Wuxian, a character in The Untamed
• YKINMKATOK = Your Kink Is Not My Kink And That's OK. Nonnies usually call this concept KINKTOMATO instead, as it's snappier and easier to remember.
• ZSS = Zhou Zi Shu, a character in Word of Honor/Faraway Wanderers

(Some content cribbed from FFA's profile page. For some concepts mentioned on this page, there may be more information at Fanlore.org.)