A word used by members of the Final Fantasy XI community, when they think of a Dragoon they laugh, hence "loldrg". It can be concidered a derogatory term towards the Dragoon job. Dragoons reputation as a job in FFXI is low, because of their relative uselessness in situations, hours spent seeking parties, and such. Instead of pointing out the reasons why a Dragoon job is weak or not so usefull, you can just say "loldrg" instead.
Other things in FFXI that players concider a joke, or weak can be said with "lol" as the prefix. loldrg was most likely the first common FFXI "lol" prefixed words.
lolpup, used in mention of the Pupeteer job, becasue of their low job reputation among the general FFXI community.
lolgenbu, used in mention of Genbu, weakest of the "Sky Gods" and most players concider him a joke.
Player 1: Looking for members for an activity!
Player 2: I'm interested!
Player 1: What job are you?
Player 2: Dragoon.
Player 1: loldrg!
Player 1: I just got killed in ballista by a Dragoon!
Player 2: loldrg!