Newcomers to codegolf.SE are often compelled to ask what many of our abbreviations and terms mean. Let us list them here so this information always will be easily available.
Abbreviations marked with a star (*) are chat specific.
*The Bakery: The Nineteenth Bakery, the room where spam and off-topic messages from The Nineteenth Byte are moved, kept as a gallery room so that users whose messages are moved aren't notified (as compared to Trash, where users get notified if their posts are moved to this room). Currently frozen.
*Butter: Spam messages, especially when moved to The Bakery. Originated from this message
Catalog: A type of simple on-topic challenge where the challenge's aim not so much to find a winner as it is to create a catalog of solutions in many languages.
CG: Code Golf; a challenge to solve a particular problem with the shortest code.
CGCC: Code Golf & Coding Challenges; our official abbreviation for the main Stack Exchange site for coding competitions.
*CMC: Chat Mini Challenge; a less formal code-golf challenge posted in chat. Answers are expected as replies to that message, and in the form
Language, XX bytes: [solution](link-to-code-running-service). Example.
*CMC / CMegaC: Chat Mega Challenge; usually a challenge posted jokingly in chat due to it being very involved or outright impossible. Example.
*<initial>MC / <language>MC: <language> Mini Challenge; Acronyms of this form are usually Chat Mini Challenges for specific languages, typically used during LYALs for that language.
*CMP: Chat Mini Poll; a request for opinions on a stated question, often about programming language design. Example.
*CMQ: Chat Mini Question; usually an alternative to a CMM, but more general (not necessarily restricted to Meta-like questions)
CnR: Cops and Robbers; challenges where one person has to "crack" another person's code.
CR: Code Review; jokingly our archenemy in the sense that they value efficient legible code while we value obscure inefficient code.
CW: Community Wiki, a type of post which especially invites collaboration editing by the community
Eleven / 11: To delete something using moderator powers, e.g. "Yeah, the post is gone, Dennis 11'd it". mod abuse -> mod abuse!!! -> mod abuse !!11!1!! -> mod abuse !!eleven!1!! -> mod abuse eleven -> eleven
FGITW: Fastest Gun in the West; a quick submission to a just-posted challenge, typically used in reference to the problem that fast answers get more visibility and upvotes than later but better ones.
Hammer: To close a challenge single-handedly; users that have a gold tag badge in one of the posts's tags have the privilege to close it as a duplicate by themselves; moderators can also single-handedly close any question.
HNQ: Hot Network Questions; a global page where popular Stack Exchange posts are often featured. Also the corresponding global sidebar.
KC: Kolmogorov Complexity; a challenge to compress a static output.
KotH: King Of The Hill; a game where the submissions interact with and compete against each other in some form of game.
*LDQ: Language Design Question; a question about some aspect of language design. Most commonly found during the Language Design Workshop but also appears during other times.
LDW: Language Design Workshop: a chat event every other Wednesday, where it is encouraged to discuss and develop your in-progress languages.
LotM: Language of the Month; a monthly event designed to promote lesser-known languages
*LYAL: Learn You A Lang For Great Good, a chat event every other Wednesday, where it is encouraged to discuss and use a specific language for that day - essentially a single day version of LotM
LQA: Low Quality Auto; these are reviews that show up in the review queue from being short or containing only code.
LQP: Low Quality Posts; posts that are generally of a very low quality, such as spam. Alternatively, used to refer to the linked review queue
Mother Meta / MSE: Meta.SE, the meta site for the entire network, where posts relevant to and about multiple sites are most on-topic.
Nuke: Moderators have the power to permanently delete a post, this is called nuking. Also used in reference to "spam nuking", where users flag a post as spam to remove it.
OEIS: The On-Line Encyclopedia of Integer Sequences; as the name says a website that collects all kinds of integer sequences and assigns them a name, e.g. the squares are A000290. Frequently cited in sequence challenges.
OWC: Objective Winning Criteria; a requirement for all challenges on the site.
PopCon: Popularity Contest; a competition where the answer with the highest vote tally (upvotes minus downvotes) wins. Note that popcons are generally discouraged, and ones that are "do X creatively" are simply not allowed.
PPCG: Programming Puzzles & Code Golf; the old name for this site.
Proper quine: A program that not only prints itself (see quine) but also obeys the proper quine rules.
Quine: A program that prints its own source code. See also proper quine.
*RO: A Room-owner of a chat room is a user with special privileges in that room.
SEDE: Stack Exchange Data Explorer, a T-SQL based website to get information about posts and other things.
Spec: Short for the specification of a challenge.
*TNB: The Nineteenth Byte; our principal chatroom.
*Twelve / *12: Similar to Eleven/11, but for room owner "abuse" in TNB instead of moderator "abuse". Often used to ask the ROs to move messages to the Bakery e.g. "@RO's can you 12 that please" in reference to a spam post.
VLQ: Very Low Quality; a type of flag that can be automatically cast on very short posts. These flags used to also cast automatic downvotes, but this no longer occurs. These also show up in the review queue.
VTC: Vote To Close; usually called a CV (Close Vote) on the rest of Stack Exchange.
VTR or VTRO: Vote To Reopen.
VTD: Vote To Delete.