Flippening refers to the moment when a cryptocurrency other than Bitcoin exceeds Bitcoin's market cap, thus flipping the mainstream cryptocurrency from Bitcoin to something else. It's an acknowledgement to the investment success and a nod to the potential investment future of the cryptocurrency world.

Most think Ethereum will surpass Bitcoin in market cap. Keep in mind that Ethereum is not a competitor currency to Bitcoin (although a lot of people and the news think that it is, incorrectly, all the fucking time.) Ethereum is not a monetary currency...it's token's value is for processing power for their blockchain platform.

Hope this helps.