The word “altcoin” is an abbreviation of “Bitcoin alternative,” and thus describes every single cryptocurrency except for Bitcoin. Altcoins are referred to as Bitcoin alternatives because, at least to some extent, most altcoins hope to either replace or improve upon at least one Bitcoin component.*
Present
The day is 13th of June 2017. The Ether market cap is rising faster than ever before. It's just a matter of days before it replaces Bitcoin's first spot.
Future
What happens next? Will Ether be mainstream like Bitcoin is now? Should we use the term altcoin at all anymore? Of course, Ethereum's development team never aimed to swap Bitcoin as a cryptocurrency but with all the problems Bitcoin is currently facing (slow and expensive transactions), it may be inevitable.
Back to the headline of this article, how should we define an altcoin now. Does it even make sense to keep the current definition (Everything that's not Bitcoin), should it be used to address cryptocurrencies below 2nd place on marketcap, or should Bitcoin be considered an altcoin when the market swaps?
food for thought