1. 
[syn: reformer, reformist, crusader, social reformer, meliorist]
2.  a warrior who engages in a holy war; 
- Example: "the Crusaders tried to recapture the Holy Land from the Muslims"
The Collaborative International Dictionary of English v.0.48:
Crusader \Cru*sad"er\ (-s?"d?r), n.
   One engaged in a crusade; as, the crusaders of the Middle
   Ages.
   [1913 Webster]
         Azure-eyed and golden-haired,
         Forth the young crusaders fared.         --Longfellow.
   [1913 Webster]
WordNet (r) 3.0 (2006):
crusader
    n 1: a disputant who advocates reform [syn: reformer,
         reformist, crusader, social reformer, meliorist]
    2: a warrior who engages in a holy war; "the Crusaders tried to
       recapture the Holy Land from the Muslims"