Middle chick is a girl your talking to that your not sure about. Sure you'd like to have sex with her but your not 100% sure about it for various reasons including how much you actually like her, how crazy she is, etc.
I been talking to Jane but ehh shes a middle chick so who knows whats going happen, shes got lots of potential.
A hardo is a person who tries extremely hard at everything. Most times a hardo will try very hard at things that do not require excessive effort. For example, sports practices, gym class, etc.
Wow did you see Jack at practice today? What a hardo!