Someone I know, who does not want to be identified in this post, was explaining to me that her new purchases were great because they looked much more expensive than they actually were. I said, "That's frontin'." She said, "What's frontin'?" I had to explain it.
I was shocked to discover that I knew someone who did not know what frontin' meant. That doesn't seem like super obscure slang. In fact, I thought it had reached the status of slang Esperanto -- which is slang so common that even middle-class white people (like me) use it without any intention of self-mockery.