MU Online glossary: all terms, acronyms and slang explained

MU Online has a rich vocabulary of slang, acronyms, and technical terms that build up over 20+ years of community. New players can feel lost in chat full of "exc+9 JoL opt," "spot stealing at Kanturu," or "guild war after CS." This glossary covers every term you'll encounter — items, classes, events, servers, PvP, and economy.

Class acronyms

All character class abbreviations:

DK   → Dark Knight (→ Blade Knight → Blade Master)
DW   → Dark Wizard (→ Soul Master → Grand Master)
Elf  → Fairy Elf (→ Muse Elf → High Elf)
MG   → Magic Gladiator (→ Duel Master)
DL   → Dark Lord (→ Lord Emperor)
SM   → Summoner (→ Bloody Summoner → Dimension Master)
RF   → Rage Fighter (→ Fist Master) — Season 9+
GL   → Grow Lancer — Season 11+
RW   → Rune Wizard — Season 16+
SL   → Slayer — Season 17+

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Evolution-specific names:

BK   → Blade Knight (2nd evolution of DK)
BM   → Blade Master (3rd evolution of DK)
GM   → Grand Master (3rd evolution of DW) — or Game Master (context matters)
HE   → High Elf (3rd evolution of Elf)
DM   → Duel Master (2nd evolution of MG) — or Dimension Master (3rd of Summoner)
LE   → Lord Emperor (2nd evolution of DL)

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Notes on class names:

"GM" is ambiguous — context matters:
→ "Our GM is a Grand Master DW" = class reference
→ "The GM banned him" = Game Master (admin)

"DM" is also ambiguous:
→ Duel Master: MG's evolution
→ Dimension Master: Summoner's 3rd evolution
→ Usually "Summoner DM" clarifies it's Dimension Master

Item terms and notation

Item quality terms:

Common  → Basic item, no special options
Exc     → Excellent: item with extra options (glows blue-gold)
Anc     → Ancient: belongs to a legendary set, activates set bonus
Socket  → Item with empty socket slots for Seed Spheres (S6 Episode 3+)
Set 380 → Highest-level base items in S6 (require level 380)

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Refine level notation:

+0 to +15 → item refinement level
+6 = "safe cap" (Bless only, no risk)
+9 = typical competitive level (requires Jewel of Soul, risky)
+11 to +13 = high-end (some servers extend beyond +9)
+15 = maximum (very rare, extreme risk investment)

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Excellent option abbreviations:

"opt" or "option" = the Excellent option itself
"2opt" = 2 Excellent options on the same item
"3opt" = 3 Excellent options (standard good item)
"max opt" = item with maximum possible Excellent options

Common excellent option abbreviations:
+DD     → +Double Damage (chance to deal double damage)
+EDR    → +Excellent Damage Rate (better: +% Max Damage in some versions)
+ID     → +Ignore Defense (ignores enemy defense — strong in PvP)
+HP     → +HP Recovery per hit / +HP increase
+MP     → +Mana Recovery per hit
+AS     → +Attack Speed
+ED     → +Excellent Defense (for armor pieces)
+Ref    → +Reflect Damage (for armor)

Example of item chat:
"EXC sword +9 3opt ID+DD+AS = 50 JoB"
→ Excellent sword, refined to +9, three options: Ignore Defense + Double Damage + Attack Speed = 50 Jewels of Bless

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Additional option (Jewel of Life):

"JoL opt" = item has an additional Life option
Life options go from level 1 to 28 (approximate)
Example: "sword +9 3opt JoL 28" = +9 sword, 3 Excellent options, max Life option

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Wing and accessory terms:

"L1/L2/L3/L4" = Wing tier
"Cape" = Dark Lord's equivalent of wings
"Exc wing" = wing with Excellent options (valuable)
"Wing +9 ID" = Wing L3 +9 with Ignore Defense option
"Pend" = Pendant (jewelry slot)
"Ring" = Ring (jewelry slot)

Event acronyms

Regular events:

BC   → Blood Castle (BC1-BC7)
DS   → Devil Square (DS1-DS7)
CC   → Chaos Castle (CC1-CC7)
CS   → Castle Siege (the biggest weekly event)
CW   → Crywolf (fortress defense event)
IT   → Illusion Temple (team PvP event, some S6 versions)
GI   → Golden Invasion (boss invasion event)

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Advanced events (S9+):

KC   → Kanturu event
MS   → Medusa (S9+ Vulcanus boss event)
AW   → Arca War (S12+ territory event)
IG   → Imperial Guardian (S13+ dungeon event)

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Event timing terms:

"BC time" = period when Blood Castle event is running
"HH" or "Happy Hour" = server event bonus period (EXP/Drop rate increase)
"Off-time" = quiet hours when fewer players are online

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Server announcements (common in chat):

"Golden Invasion!" = Golden monsters appeared — farm now
"Blood Castle starts in 5 minutes" = get your ticket
"Castle Siege has ended!" = winner announcement

Server terminology

Server administration terms:

GameServer   → The main server executable that runs MU Online (called "GameServer.exe")
DataServer   → The database connection server
ConnectServer → Controls client connections and authentication
WebServer    → The management web panel (some server setups)
GM           → Game Master = the server administrator or admin account

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Server types:

EXP rate (or "rate"):
→ The multiplier applied to base experience gain
→ x1 = official speed, x100 = 100 times faster
→ Common: x300 (medium), x500-x1000 (fast), x5000+ (fun)

"Drop rate":
→ Multiplier applied to item drop chance
→ Higher rates: more Excellent and Jewel drops per hour

Server style abbreviations:
→ "PvM" = player-vs-monster focus (farm-heavy)
→ "PvP" = player-vs-player focus (combat-heavy)
→ "Slow" = x1-x15 EXP (months to max level)
→ "Mid" = x100-x300 EXP (weeks to max)
→ "Fun" / "Fast" = x500-x5000 (days to max)

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Season and version terms:

S6   → Season 6 (most common private server version)
S6ep3 → Season 6 Episode 3 (the complete version of S6)
S9   → Season 9 (added Rage Fighter)
S12  → Season 12 (added Pentagrama, Muun, Errtels)
"Wipe" → Complete reset of all character data
"Relaunch" → Server wipe + fresh start, often with balance changes

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Anti-cheat and server management:

"Anti-hack" = cheat protection system
"No-IP" = Dynamic DNS service (allows server to have a domain without static IP)
"FTP" = File Transfer Protocol (used to manage server files remotely)
"VPS" = Virtual Private Server (cloud server used to host MU)
"Dedicated" / "Dedi" = Dedicated server (physical machine, more stable than VPS)
"BAN" = account/character banned by admin
"KICK" = forced disconnect from server

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Technical game files:

"MuServer files" = the collection of executables and config files that run the server
"GameServer.ini" = main configuration file for game server
"DataServer.ini" = database connection config
"BannedIPs.txt" = admin file of blocked IP addresses
"SQLServer" = the database engine (Microsoft SQL Server or MySQL)

Progression and build terms

Character progression:

Reset     → Zero your character level back to 1 (keep stats or get points)
"R1" = 1 reset, "R5" = 5 resets — shorthand for progression stage
GR        → Grand Reset: reset your resets (available on some servers)
ML        → Master Level: post-cap progression system in S6
"Cap"     → Maximum level (varies by server: 400, 500, etc.)
"Max level" → Reached the server's experience level cap

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Stats and build terms:

STR → Strength: physical damage, equipment requirement
AGI → Agility: attack speed, defense, evasion (also "Dex" on some interfaces)
VIT → Vitality: HP pool
ENE → Energy: magic damage, Mana pool
CMD → Command: Dark Lord exclusive, increases max guild members

"Full VIT" = character with all points in Vitality (maximum HP — very tanky)
"Full STR" = character with maximum Strength (maximum physical DPS)
"Balanced build" = points split between STR/AGI or ENE/VIT
"Hybrid" = character using both physical and magic (MG specialty)

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Build terms:

PvM build = optimized for fighting monsters (farming focus)
PvP build = optimized for player vs player combat
Support build = Elf focused on buffs rather than damage
"Glass cannon" = very high damage, very low survivability
"Tank" = prioritize HP and defense over damage

Economy and trade terms

Currency and value:

JoB    → Jewel of Bless (informal currency in S6)
JoS    → Jewel of Soul
JoL    → Jewel of Life
JoCh   → Jewel of Chaos
JoCr   → Jewel of Creation
Zen    → The in-game money (used for NPC purchases, crafting fees)

Trade terms:
"WTB"  → Want to Buy
"WTS"  → Want to Sell
"WTT"  → Want to Trade
"PC"   → Price Check ("PC on this exc sword?")
"BO"   → Buy Out (best offer)

Price discussion:
"Nego" → Negotiable (price can be discussed)
"Fixed" → Non-negotiable price
"Rip" → Too expensive ("That price is rip = overpriced")
"Cheap" → Good deal

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Trade safety terms:

"Safe trade" = using in-game trade interface (verified simultaneous exchange)
"Trade window" = the game's built-in secure trade system
"Drop trade" = dropping items on the ground to trade (risky — don't do this)
"Scam" = someone who takes your items without payment
"Trust trade" = trusting someone to send items first (very risky)

PvP and combat terms

PvP (Player vs Player) terms:

PK        → Player Kill: killing another player
"PK'd"    → Got killed by another player
"PKer"    → Someone who actively hunts and kills other players
"PK mode" → Character is in "kill on sight" mode (dark-colored name)

Character status based on PK count:
→ Neutral: white/normal name
→ Outlaw: orange/yellow name (few PKs)
→ Killer: red name (many PKs)
→ Murderer: dark/black name (maximum PK count)

PK consequences:
→ Red/murderer names: other players can attack them freely
→ Death while PK: drop chance of equipped items (server-dependent)
→ "No drop" servers: items don't drop on death

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PvP action terms:

"Kill steal" / "KS" → Killing a monster another player was fighting to steal the drop
"Spot steal" → Taking over someone's farming spot by killing their monsters
"Hunt" → Actively seeking and killing a specific player
"Flag" → Challenge someone to a duel
"War" → Official Guild vs Guild PvP declared state
"Buff steal" → Using another class's buff without permission (Elf buffs are public)

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Guild PvP terms:

"Guild war" → Formal declaration of war between two guilds (PvP without PK penalty)
"Alliance" → Two guilds allied (not enemies, cooperate in CS)
"Betrayal" → Guild member leaving to join rival guild mid-conflict
"Mercy" → Agreeing not to PK someone (usually weaker players)

See also the beginner's guide (how to start playing MU Online), the items guide (Excellent, Ancient, and Socket Items in detail), and the events guide (BC, DS, CC, CS in detail for the event terms used in this glossary).

Frequently asked questions