A pretty girl that has no common sense.
Growing up this is what I called my sisters and they called all the other girls. We knew what a chachi was (over-dressed spanish/white trash) trying to be something different....and we just assumed everyone else knew. Sadly, now that I have kids (all girls) this is what I call them. It is now a "term of endearment" that I use for them...they are adorable and smart, but when they are not paying attention or do something totally unexpected...chachi loo is what comes out! :)