Healadin is a term used by some people for paladins that have specialised their character in healing. They will wear pieces of armour that give advantages to intellect and spell power and will have spent talent points deeply into the Holy tree. Healadins are also typical Pocket Healers in Battle Grounds, and their plate armor and Divine Shield makes them hard to kill.
Prior to the release of The Burning Crusade, the superiority of the healing bonuses to certain pieces of cloth armor, may have led some healadins to wearing cloth. Healing paladins wearing cloth are often referred to as clothadins.
See also: Paladins as healers, Healadin Sets