jackal

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Any of several mammals of the genus Canis of Africa, Asia, and southeast Europe, that are chiefly foragers feeding on plants, small animals, and occasionally carrion.
• noun One who seeks to gain advantage or profit from the difficulties of another.
• noun One who performs menial tasks for another.

from The Century Dictionary.

• noun A kind of wild dog somewhat resembling a fox, which inhabits Asia and Africa; one of several species of old-world fox-like Canidæ, of the genus Canis, as C. aureus of Asia, or C. anthus of Africa.
• noun Hence Any one who does dirty work for another; one who meanly serves the purpose of another.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Zoöl.) Any one of several species of carnivorous animals inhabiting Africa and Asia, related to the dog and wolf. They are cowardly, nocturnal, and gregarious. They feed largely on carrion, and are noted for their piercing and dismal howling.
• noun colloq. One who does mean work for another's advantage, as jackals were once thought to kill game which lions appropriated.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun Any of several wild canine species, native to the tropical Old World, smaller than a wolf.
• noun A person who performs menial/routine tasks, dogsbody
• noun pejorative A person who behaves in an opportunistic way; especially a base collaborator.
• noun slang, rare A jack (the playing card.)
• verb To perform menial or routine tasks

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun Old World nocturnal canine mammal closely related to the dog; smaller than a wolf; sometimes hunts in a pack but usually singly or as a member of a pair