There are a lot of terms used in the online LEGO community which may be unfamiliar to some of you. Here are some of the commonly used terms. Feel free to post if you have a suggestion for more term(s) to be added or if you have a question about a term not included.

Thanks to Akunthita for a lot of these terms and to DarkZephyr for helping with organization

A
-AFAIK: As Far As I Know.
-AFOL: Adult Fan of LEGO.
-ALE: Adult LEGO Enthisiast.
-ASAP: As Soon As Possible.
-ASO: All Studs Out. Sometimes called SAO, Studs All Out (a building method)

B
-BC: Brick Con, a LEGO convention. Also refered to as NWBC.
-BF: BrickForge, the company with the greatest custom parts out there! Also: BrickFest, one of the largest LEGO conventions.
-BL: BrickLink, a large web site with a LEGO reference catalog and the largest online LEGO market.
-BM: BrickMaster or Batman
-BS: BrickShelf, a free LEGO image hosting site.
-BTW: By The Way.
-BURP: Big Ugly Rock Piece.
-BW: Brickworld, an annual LEGO convention in Illinois.

C
-CC: Classic-Castle.com. A large online LEGO Castle community.
-CRAPP: Crummy Ramp And Pit Plate.

D

E

F
-FAQ: Frequently Asked Questions.
-FFS: For freaking sake.
-FFOL: Female Fan of LEGO
-FTR: For The Record
-FTW: For The Win

G

H
-HP: Harry Potter.
-HTF: Hard To Find.
-HOG: Hand of God - when you move minifigs around, they think it is God moving them around.

I
-IIRC: If I Recall Correctly.
-IJ: Indiana Jones.
-IMHO: In My Humble Opinion.
-IMO: In My Opinion.
-IYDK: If You Didn't Know

J

K
-KABOB: Kid with A Bunch Of Bricks.
-KK: Knights' Kingdom (2000).
-KK 2: See: KK II.
-KK I: See KK.
-KK II: Knights' Kingdom II (2004). Unrelated to Knights' Kingdom (2000).
-KUTGW: Keep Up The Good Work.

L
-LEGOECTOMY: A procedure where a Lego piece is removed from a body cavity [i.e. ear, nose, mouth, belly button etc]. This usually involves the help of two adults and one fairly panic-stricken child. It's unknown why children feel the need to insert Lego pieces into body parts but knowing how to react to these situations can mean the difference between a few seconds of discomfort and a trip to the emergency room. To read more about Lego element removal, you can read an editorial entitled http://www.epinions.com/kifm-review-7C9 ... C6E9-prod3
-LL: LEGOLAND.
-LOL: Laugh Out Loud. A very common term used online to show amusement.
-LOTR: Lord of the Rings.
-LU: LEGO Universe. A LEGO MMORPG being released soon.
-LUG: LEGO Users Group.
-LURP: Little Ugly Rock Piece.

M
-MCN: Minifig Customization Network. A large online community dedicated to making custom minifigs.
-MISB: Mint In Sealed Box.
-MISP: Mint In Sealed Package.
-MMOG: Massive Multiplayer Online Game.
-MMORPG: Massive Multiplayer Online Role Playing Game.
-MOC: My Own Creation. Term describing any creation built by a LEGO fan as opposed to TLC.
-MOTD: MOC Of The Day. Each day MOCpages.com has a featured MOC.

N
-NLP: Non-Lego Parent or Person (A term for someone that isn't familiar with Lego terminology, sets or building applications.)
-NPB: Non-Paying Buyer.
-NRS: Non-Responding Seller.
-NSS: Non-Sending Seller.
-NWBC: North-West Brick Con, a LEGO convention. Also refered to as NWBC.

O
-OMG: Oh My Gosh.
-OOS: Out Of Stock.
-OOP: Out Of Package.

P
-PAB: Pick-A-Brick.
-POOP: Parts Of Other Pieces. Pieces that can be made from other pieces, such as the large pieces in the 4 Juniors, Jack Stone, etc. themes.

Q

R
-ROFL: Roll On the Floor Laughing.
-ROTFLOL: Roll On The Floor Laughing Out Loud.
-RPG: Role Playing Game.

S
-S@H: Shop@Home. The official online LEGO Shop.
-S&H: Shipping and Handling.
-S/H: S@H or S&H.
-Sigfig: Signature Minifigure. Some people choose to make a minifig to represent themselves in the LEGO universe, sometimes even several for different themes and eras. (i.e. sci-fi, castle, Star Wars, etc.)
-SNOT: Studs Not On Top.
-STAMP: STicker Across Multiple Pieces.
-SW: Star Wars.

T
-TLC: The LEGO Company. Synonymous with TLG.
-TLG: The LEGO Group. Synonymous with TLC.
-TRU: Toys R Us
-TFOL: Teen Fan of LEGO

U
-UCS: Ultimate Collector's Series

V

W
-WIP: Work In Progress. Used to describe a MOC or custom that is started but not yet complete.
-WTB: Want To Buy

X

Y

Z
-ZOMG: Zoh My Gosh

Thank you so much! This is very useful! A great reference!
Thanks!

what are MCN and CC?

Uhm....sorry for my ignorance, but what is a SIG-FIG? Would you let me know? And maybe ad it to the list?

signature-minifigure

SO thaats what MoC means. it still seems lacking though, Im still finding terms I don't know...

also wondering what ffs and BL are

Yes, sig-fig is signature minifigure, thank you Metagross. FFS means for freaking sake. BL means BrickLink. (it is on the list already). CC is Classic-Castle, a large LEGO castle web site. MCN is Minifig Customization Network. I will add these terms to the list.

Maybe add WIP

Oh, how COULD I forget that? Thanks for reminding me of that crucial term!