When the Soles of the feet are blackened or dirty.
The "hippie feet" phenomenon mainly occurs on the bottom of the foot. Primarily caused by bare feet walking on blacktop or any other filthy ground surface.
It is important to note that having hippie feet does not make you a hippie ... just means you gotta wash your feet and at least wear sandals whilst in public.
1. I lost my sandles at the beach, so I had to walk back to the car barefoot, and now I have a bad case of the hippie feet.
2. Yeah her toenail polish was cute, but that is totally negated by the hippie feet.
3. Hunny... I know you hate it when I have hippie feet, but you're gonna have to deal with it because it's hot and shoes are too cumbersome right now.