Usually a latina girl, but could be any nationality, is a female who thinks she's the shit and dresses like a hoochie mama all the time, even if she's just going to the store. For example, showing up at community college dressed like she's at a fucking club. And strutting her shit around to make sure the guys are looking, because her egotistical personality needs the attention.
Cha chas tend to wear open-toed shoes, flip-flops, and chancletas.
"I'm not going anywhere with you dressed like that! You look like a cha cha."
"Look at that cha cha over there. That fatty shouldn't be wearing a tank-top!"