Technically means a dark skinned woman with large nipples, but you can use it as an insult whenever you wish. A great word to add to your arsenal.
"You are such a fucking nube!"
"Wow, nube, go get pwned..."
Nube: Y0u 5UCK!!!! Y0uR G3ttiiNG LuCKy!!!! 0NCE I G3T A G3RN4DE L4UNCH3R your going downtown!