The act of not wearing shoes, anywhere you go, weather it be by accident or on purpose.
"Man, I lost my sandals like a week ago, and I've been going flintstone ever since!"
"Some one barfed on my shoes @ the rave last night, I had to go flintstone till 6 am! Do you know how disgusting that was?"
My neighbor came out of his house with an uber-rib in his hand, bbq sauce on his face and no shirt. He then walked his dog down the street going flintstone. And he wonders why we all talk about him!