Derogatory term for a Retribution Paladin, dating back to 2011. Paladin's DPS at the time lower than average, making playing the class in a DPS spec the poorer choice over the more useful Healer, or Tanking specs. Players who insisted on the Retribution spec despite the shortcomings were thus referred to as "Loladin," "Retardin," etc.
Although Blizzard have since re-balanced all three Paladin specs, "Loladin" has become more of a nostalgic, affectionate term for Retribution Paladins.
Paladin 1: What spec you been leveling in?
Paladin 2: Loladin..