The Collaborative International Dictionary of English v.0.48:

Marauder \Ma*raud`er\, n. [From Maraud, v.: cf. F. maraudeur.]
   A rover in quest of booty or plunder; a plunderer; one who
   pillages. --De Quincey.
   [1913 Webster]

WordNet (r) 3.0 (2006):

marauder
    n 1: someone who attacks in search of booty [syn: marauder,
         predator, vulture, piranha]

Moby Thesaurus II by Grady Ward, 1.0:

24 Moby Thesaurus words for "marauder":
   bandit, brigand, buccaneer, bummer, depredator, desperado,
   despoiler, forager, forayer, freebooter, looter, pillager, pirate,
   plunderer, raider, rapparee, ravager, ravisher, reiver, rifler,
   sacker, spoiler, spoliator, wrecker



Bouvier's Law Dictionary, Revised 6th Ed (1856):

MARAUDER. One who, while employed in the army as a soldier, commits a
larceny or robbery in the neighborhood of the camp, or while wandering away
from the army. Merl. Repert. h.t.