Here I will list most of the commonly used acronyms and abbreviations you will undoubtedly encounter.
SH = Shadow Hunter
Sin = Assassin
DM = Dark Magician
WL = Warlock
Sorc = Sorcerer
BS = Battle Summoner
HW = Holy Warrior
Bish = Bishop
SPS = Spirit Singer
Huna = Kahuna
Champ = Champion
BH = Battle Huna
SB = Soul Breeder
CM = Chaos Magician
WTS = Want to Sell
WTB = Want to Buy
WTT = Want to Trade
SS = Stamina Saver
Pot = Potion
Epro = E-Protect
1H = One-Handed (Refers to weaponry)
2H = Two-Handed (Refers to weaponry)
E. Orc (Or any other pet) = Empty Orc. Refers to the pet card.
DD = Damage Dealer
LFDP = Looking for Dungeon Party
M1 or M2 = Relic of Arid Moonlight (1) or (2)
LM1 or LM2 = Lost Mines (1) or (2)
CV1 or CV2 = Crystal Valley (1) or (2)
PP1 or PP2 = Shrine of Palmir Plateau (1) or (2)
ToA1 or ToA2 = Temple of Ancients (1) or (2)
Con1-5 = Controllers 1 through 5.
Rep = Replacement
TB = Town Break