Altcoins originally meant "Bitcoin alternatives" because in the early stages of cryptocurrency development, every blockchain-based currency was viewed as a Bitcoin imitation. Cryptocurrencies at that time were mainly used for payments, LTC, XRP and Peercoin (PPC). Altcoins are used as a general term for cryptocurrencies other than Bitcoin.

If "altcoins" refer to non-Bitcoin cryptocurrencies that have the same characteristics as Bitcoin, then this definition certainly no longer fits all of the 20,000+ cryptocurrencies out there.

The evolving definition of altcoins is now more precise – generally referring to alternative coins within a specific niche. Altcoins are often more advanced in terms of technical features or ecosystem applications, but so far, no altcoin has come close to surpassing Bitcoin in terms of consensus, ubiquity, or market capitalization.