Pick your dictionary: I'm partial to the AHD because it gives you both def. and etym. in one groovy swell foop.

NOUN: Inflected forms: pl. mon·goos·es
Any of various Old World carnivorous mammals of the genus Herpestes and related genera, having a slender agile body and a long tail and noted for the ability to seize and kill venomous snakes.

ETYMOLOGY: Marathi mangus, of Dravidian origin.

http://www.bartleby.com/61/63/M0386300.html