These emojis: 🚌 🏫 🧠 will represent what game these Abbreviations / Acronyms are used in / Associated with.
🚌 - Used only in Limbus Company
🏫 - Used only in Library of Ruina
🧠 - Used only in Lobotomy Corporation
🌙 - Used in 2 or more Project Moon games

Pls remember that this guide isn't finished yet
Feel free to add any other stuff i missed in the comments

🌙 AOE - Area of Effect (i added this incase some people dont know what AOE means, ik its unrelated)
🌙 BGM - Background Music
🌙 BL - Blade Lineage
🚌 BP - Battlepass
🚌 C1, 2, 3... - Canto / Chapter 1, 2, 3...
🌙 DPS - Damage Per Second (Usually used to describe a damage-dealer)
🌙 EGO - Extermination of Geometrical Organ
🚌 Fell - Fell Bullet
🚌 FG - Fanghunt
🌙 FS - Full-stop
🌙 Frei / Der Frei - Der Freischutz
🌙 HP - Health Points
🚌 ID - Identity
🌙 KK - Kurokumo Clan
🌙 KOD - Knight of Despair
🌙 KOG - King of Greed
🚌 LCA - Limbus Company ? ( I don't know what this is)
🚌 LCB - Limbus Company Bus
🚌 LCC - Limbus Company Clearance
🚌 LCCB - Limbus Company Clearance Before (team)?
🚌 LCCA - Limbus Company Clearance After (team)?
🚌 LCD - Limbus Company (Distortion (team))?
🚌 LCE - Limbus Company Enkephalin
🏫 LOR - Library of Ruina
🌙 MB - Magic Bullet
🚌 MC - Multicrack
🚌 MD - Mirror Dungeon
🌙 MOSB - Mountain of Smiling Bodies
🚌 MOTWE - Murder on the Warp Express
🌙 NT - Nothing There
🌙 OP - Overpowered
🌙 PB - Punishing Bird
🌙 PM - Project Moon
🏫 PT - Purple Tear
🌙 QOH - Queen of Hatred
🚌 RB - Ryoshu's Bistro
🚌 RR - Refraction Railway
🚌 RS - Red Sheet
🚌 S1, S2, S3 - Skill 1, 2, 3
🏫 SOTC - Star of the City
🌙 SP - Sanity Points
🌙 T-Corp - Timetrack Corp.
🚌 UT - Uptie
🏫 VC - Vermilion Cross
🚌 WH - Wild Hunt
🚌 WN - Walpurgisnacht / Walpurgis night