joey

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

• noun A young marsupial, especially a baby kangaroo.

from The Century Dictionary.

• noun In coal-mining, a man specially appointed to set the timber in a stall or working while coal is being raised.
• noun Same as joe, 1.
• noun A young kangaroo.
• noun ‘A hewer of wood and drawer of water.’
• To insult (a person) by the cry of ‘joey.’

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

• noun Australian Any young animal, especially a young kangaroo.
• noun Australian A young child.
• noun British slang A three-penny piece.

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

• noun The immature young of a marsupial, notably a junior kangaroo, but also a young wallaby or koala etc.
• noun The shorter word whose letters can be found within a kangaroo word.