A Mangina is a self-depreciating man who subconsciously hates himself and blindly believes women are superior to him. He has been raised to think masculinity is inherently wrong - perhaps even a genetic/evolutionary/social flaw - and must be corrected by embracing his "feminine side" to the point of losing the very qualities that make him male. He believes women are beautiful, innocent angels and men are filthy animals who need to be controlled.
Patrick Carey (PK) loves white knighting for women, he's such a mangina.
When employees and higher ups from Circuit City force everyone out of another company to bring in their own ex-Circuit City employees. The term implies that they just then stand around in a circle jerk to celebrate their success of eventually bringing utter failure to the company that they are invading.
Dude I just lost my job to a Circuit Jerk.