This list is constantly evolving as I think of more lingo to add, and as I learn more myself. If you don't see something on the list that you think should be included, feel free to let me know!
AC - Usually refers to Aquaclear HOB filters of any model.
bb - Sometimes beneficial bacteria is abbreviated as such.
bbr - Brown baby ranchu; describes the bronze color that young fry still have usually under 2 months of age.
bbs - Baby brine shrimp; a favorite food for goldfish fry.
BEP - Blue egg phoenix goldfish.
Bristol - Refers to the bristol shubunkin; a type of shubunkin with a tail that is heart-shaped with rounded lobes.
bs - Brine shrimp.
Butterfly - Refers to the butterfly tail telescope; a type of telescope eye goldfish that has a tail resembling the outstretched wings of a butterfly from above.
cbr - Color baby ranchu; when they start to color up (change from bronze/green to their adult color) around 2-4 months.
Dechlor - Dechlorinator.
DO - Can mean dissolved oxygen or Dandy Orandas.
Drop test - This is a type of water test (either ammonia, nitrite, nitrate, pH, KH, or GH) that is more reliable than the test strip type. The most-used brand is API (Aquarium Pharmaceuticals Inc.).
Epsom - Epsom salt; magnesium sulfate (MgSO4). Found in most grocery stores or general stores in the laxatives section.
fbs - Frozen brine shrimp.
fbw - Frozen bloodworms.
Fork or forking - The part of the caudal fin which forms a v-shaped indent back toward the body of the fish. Fish like ribbontails have a very deep fork, whereas veiltails have no fork.
Gel food - Gel food is a soft, often homemade food that can be made or purchased for goldfish. It's called gel because it's almost always made with gelatin as the binding agent.
GH - General hardness; refers to the concentration of calcium and magnesium in the water.
GHV - Goldfish herpes virus.
gw - Green water; refers to water that is tinted green because of suspended algae growing in it.
HOB - Hang on back filter. This is a type of power filter that rests on the rim of the aquarium and hangs over the back.
KH - Carbonate hardness; refers to the concentration of bicarbonate and carbonate in the water.
lbbs - Live baby brine shrimp.
LPS - Local fish store.
MMs or mms - This refers to MetroMeds; a common antibiotic food for goldfish.
NLS - New Life Spectrum goldfish pellet food.
Params - Parameters; referring to the water parameters. This means: ammonia, nitrite, nitrate, pH, KH, GH, and sometimes temperature too.
Pineconing or pineconed - When the fish is bloated such that the scales stand on end. The fish resembles a pinecone when viewed from above.
Prazi - Praziquantel; an anti-parasite medication useful against gill and body flukes. AquaPrazi is one commonly used powder form, and PraziPro is the most commonly used liquid form. The liquid form is easier to use, but the powder may be more convenient for large tanks or ponds.
Prime - A dechlorinator and ammonia/nitrite detoxifier made by Seachem.
QT - Quarantine; this can refer to quarantine on a brand new fish, or quarantine when a certain fish is showing signs of disease and needs to be isolated.
Repashy - This refers to a line of premixed gel foods made by Repashy Superfoods. The most commonly used mixes for goldfish are Soilent Green and Super Green.
Salt - This refers to pure salt; sodium chloride (NaCl). Some commonly used forms are: Morton Canning and Pickling salt, sea salt, and aquarium salt. It must have no anti-caking agents, iodide, or other additives.
Scope - Microscope.
Scrape - Gently scraping a fish with a microscope slide in a specific area in order to get a sample for viewing under a microscope.
Shu - Shubunkin goldfish.
Soilent Green or SG- A premixed gel food made by Repashy Superfoods.
SVCV - Spring virema carp virus.
SVR or svr - Side view ranchu. A specific breed of ranchu; Chinese in origin, which is meant to be viewed from the side.
TMS - Caribsea Tahitian Moon Sand.
TVR or tvr - Top view ranchu. A specific breed of ranchu; Japanese in origin, which is meant to be viewed from above.
VT - Veiltail goldfish. The veiltail has extra long fins, and the caudal fin should have no forking.
w/c or wc - Water change.
I picked up a lot of this information over time on Goldfish Keepers Forum. Head on over and check it out!