One who is Chinese and Cuban ethnicity. Sometimes people generalize asians and hispanics (ie: calling someone chinese even though they are korean or from some other part of asia, or calling someone Mexican even though they are Puerto rican etc etc.)
Can also be used as slang for "you been". see Example #2.
#1: Tabitha, are you eating fried rice and tacos? You are SUCH a chuban.
#2: Hey! Long time no see!! What chuban doin!?" This can be confusing as one might wonder if you mean "Hey, what have you been doing" or "Hey what is Tabitha (the chuban wonder girl) doing?"
Live it. Learn it. Love it.