A girl under the age of 18. (actually anyone under 18); Minor in the U.S. When informing another unknowing person that the girl they are peeping is under age you tell them, "she's tu yong" aka too young, with a Chinese accent to make this sometimes awkard moment funny yet surreal. Having sexual relations with a young girl is illegal and get you thrown in jail, you caught the Chinese Disease.
Pancho: Whatcha lookin at dude?
Theodore: Dat chick over there, man she's fine.
Pancho: Hey, she's got that Chinese Disease, better stay away.
Theodore: What is that, is she from China?
Pancho: No, homeboy she's tu yong.
12 step recovery jargon referring to someone new who talks about how great life is, now that they'resober. Usually meaning that the person is out of touch with reality.
The new guy seems pretty happy for a dude who has no job, no money and no family. He must be on a pink cloud.