The Collaborative International Dictionary of English v.0.48:
Pillager \Pil"la*ger\, n. One who pillages. --Pope. [1913 Webster]WordNet (r) 3.0 (2006):
pillager n 1: someone who takes spoils or plunder (as in war) [syn: plunderer, pillager, looter, spoiler, despoiler, raider, freebooter]