Units - The length of each cap is determined by “units”. Shown as the number of units followed by a lowercase “u” most of the time. All the alphabetical caps are 1u.
Legends - The letters or icons on the actual keycap.
Sublegends - Legends that are secondary to the main legend. Usually another language.
Stepped Keys - Caps that have a step on the right side of them.
Sculpt/Sculpted - Some keycaps are different heights and angles on each row to create a sculpted profile for a more comfortable typing experience.
Uniform - When a profile is the same angle and height on each row to create a uniform typing experience with no sculpt. A common uniform profile is DSA.
Rows - Each row of a sculpted profile is numbered. R1-R4 are the standard rows but some sets include row R0-R5.
Cylindrical - This describes keycap profiles where the top of the keycap where your finger touches is "cutout" of the cap in the shape of a cylinder on its side. The most popular cylindrical profile is Cherry.
Spherical - This describes keycap profiles where the top of the keycap where your finger touches is "cutout" of the cap in the shape of a sphere on its side. The most popular cylindrical profile is SA.
QMK - Quantum Mechanical Keyboard. Open source programming firmware. Go here for more details.
VIA - User Interface for programming and testing QMK-compatible PCBs. Go here for more details.
MOQ - Stands for "minimum order quantity" and designates the minimum number that must be ordered for the product to be produced.
Interest Check (IC) - A public post on a forum or website to test the interest of a product to see if it should be produced and get feedback for possible changes and/or improvements.
Groupbuy (GB) - Similar to preorder, but is run prior to the product being purchased/manufactured. A groupbuy window is open for a stated amount of time with the goal of reaching the minimum order quantity for the production of a product. Order now, receive later (normally months to a year). Often, groupbuys will be discounted from the MSRP because of the wait time and support of the project. Go here for more details.
FCFS - Stands for "First Come, First Serve". Product sales method where items are sold on a website for whoever can check out first. The traditional way that most businesses sell things.
Raffle - Product sales method where items are sold via a lottery of random winners after a defined window period is over (as opposed to FCFS, speed does not matter). Customers enter their names into the raffle hoping to be randomly chosen to be able to purchase the item. This method is usually seen as more "fair" than FCFS.
Vickrey - Auction style buying of boards, where the 2nd top bid is used to define the buying price. Go here for a more detailed explanation.
Private Buy - Also commonly called a "Proto Buy". A small closed groupbuy with a few people to test manufacturing or just a very close group of people wanting a specific board.
OOS - Out of Stock
NE - Any
Avail - Available
Keeb - A shortened word for keyboard
Stab - Stabilizer
Thock - An onomatopoeia describing the highly sought-after sound a switch makes when bottoming out.
OP - Original Poster. OP is the person who started a thread or comment.
Flipping - Selling for profit. Highly frowned upon for the most part in the community.
r/mechanicalkeyboards (r/mk, rmk) - A community subreddit on Reddit dedicated to mechanical keyboards.
r/mechmarket (r/mm, rmm, mm) - A community on Reddit dedicated to the buying, selling, and trading of keyboard-related items.
geekhack (GH) - One of the most popular forums for mechanical keyboard enthusiasts.
Deskthority - Forum with a primary focus on vintage mechanical keyboards and documentation of keyboard information.
Deskthority Wiki - A wiki containing research on especially older keyboards and switches, useful for identifying a vintage board and/or its switches.
Keebtalk - A Discourse-based forum created by Huey Hoang (Manofinterests), Andrew Lekashman (Input Club CEO), Ryan Norbauer, Olivia Briggs, and Nathan Kim after geekhack was acquired by Drop.