As promised.
MOC
A creation made out of LEGO or BIONICLE. MOC stands for My Own Creation. This term can be used to refer to another's MOC, although if interpreted literally, it will not make sense. MOCists have learned to wisely ignore the literal qualities of the term. Pronounced "mock", and is always capitalized. In terms of pluralization, it is MOCs, without an apostrophe.
MOCist
One who engages in the activity of MOCing. Also known as a MOCer, or "weird".
MOCing
Constructing an original model out of BIONICLE or LEGO, an activity which should not be constantly interrupted. Doing so will result in Revenge.
Revenge
Turning another's socks inside out, laughing maniacally, and hiding random objects from sight.
MOCer's Conversation
Otherwise known as a "generic conversation", it can be easily recognized if the MOCer uses generic phrases and replies such as "mmhmm" "not really" "that depends" "sure" and "of course" When you find yourself engaged in such a conversation with a MOCer, it's usually a sign that the MOCer doesn't want to be disturbed. EDIT: Arpy has kindly given me an example of what happens when two MOCers meet. I quote him here:
Silence
Consists of loud shuffling sounds similar to that made by rummaging through buckets of LEGO, popping sounds similar to studs being connected, or ball joints being attached to sockets.
Annoyance
Consists of anything that constantly interrupts the MOCer from the activity of MOCing.
A Piece Kind Of Like This, But With This Over Here, And That An Axle Hole, And This One Stud Over.
A part that many a good MOCer has wished for, but it sadly doesn't exist, driving the MOCer insane.
The Right Piece
The one part that the MOCer doesn't have, either in the right color, or doesn't exist, or comes on a set retired in 1997-2004.
Aagh!
An expression uttered when the MOCer encounters A Piece Kind Of Like This, But With This Over Here, And That An Axle Hole, And This One Stud Over, or The Right Piece.
Space
Something which doesn't exist to the MOCer.
Greeble(s)
1. Small details to add to the complexity of the model, usually reserved for larger models.
2. Something which looks cool but doesn't really do anything.
3. Anything extra to fill in blank spaces on a MOC.
Dark Gray/Black
Two colors which often get confused in instruction books, resulting in mass confusion.
Technic Bracing
Something the MOCer wishes he/she would have incorporated into a larger model before attempting to pick it up.
Loud Screams/Shrieks
Something which occurs after the MOCer tries to pick up a large model without Technic Bracing.
Chrome
A color of element which is rare and expensive to the MOCer. Chrome is to the MOCer what gold is to the Miner.
Two Of These
Something the MOCer says after you ask them what part they need. Chances are that the part is The Right Piece.
And a definition for Arpy:
Custom
An overrated adjective. Refers to any part of the MOC that is built entirely on an original or popular design. This term is most often used by people who can't MOC, and try to discredit a MOCer's skills by pointing out parts of the MOC that are lacking "custom" in any way, to make the non-MOCer feel better about his own really lousy MOCing skills. Those who can't do, teach.
What?
A term used by the MOCer when a non-MOCer says that the MOCer's MOC isn't "custom"
Cordak
A piece hated by many MOCers. Used as an insult.
Zamor Sphere
A piece that hurts like everything when you kneel on it.
Aiigh, gurgle dang zurgle zamor gahh!
A phrase used by the MOCer immediately after kneeling on a zamor.
Black two-length axles
A part which is now becoming an endangered species. The MOCer never has enough of these.
Nuju
Something you don't want to step on in the middle of the night, lest you mistakenly assume that a cactus has taken up a home in your room.
WIP
Stands for Work In Progress, reffers to anything that the MOCer is too lazy to finish, but would rather waste their time taking pictures of the inside of the model and uploading them to brickshelf, so everyone can see the ugly, unfinished MOC.
Feel free to add more, but when refering to another definition in the dictionary, (Aside from MOC, MOCist, (MOCer) or MOCing) put it in italics or bold, to make the reference clearer.
Also, you notice that for Arpy's sake I changed all the "MOCist" to "MOCer", except for the main definition.