Here's a list of slang and expressions that Japanese people use on the Internet:w (笑) - it's the first letter of verb 笑う (warau) which means "to laugh". "w" is the same as "lol" in English.
GBK (ごばく) - it comes from word 誤爆 (gobaku) which means "false explosion". "gbk" is the same as "wrong chat" in English.
狩り (kari) - it means "hunting". It's the same as "training" (killing monsters to get experience points).
サブ (sabu) - it's "alternate character" (alt).
PT (パーティトレーニング) - it means "party training".
TKM - it comes from word 特務 (tokumu) which means "special investigation". It's the same as "instance".
援軍 (engun) - it means "reinforcements". It's the same as "respawn".
ORZ - a posture emoticon representing a kneeling, bowing, or comically fallen over person.
4649 (よろしく) - "yoroshiku" (derived as follows: "yo" (4) "ro" (6) "shi" (4) "ku" (9)). Meaning in this topic:
https://archanea.darkbb.com/t31-japanese-greetings求) (求め) - "motome" means "request". People use it when they want to buy an certain item on world chat.
出) (出す), 売) (売る) - "dasu" or "uru" means "to sell".
買) (買う) - "kau" means "to buy".
売り切れました - "urikiremashita" means "sold out".
Here's a template if you want to buy something on auctions:求)ITEM 出)PRICE 競売お願いします
After buying, type "ITEM〆ます".
It means that you've already bought the item.