Altcoin is short for “Alternative” Coin. Alternative coins are all the coins or tokens in cryptocurrency, except Bitcoin.
The reason is that Bitcoin is considered as main cryptocurrency (being the first one) and all the subsequent coins & tokens are alternative to Bitcoin.
Is Etherium an Altcoin?
Yes, Etherium is an altcoin by the standard understanding of every non-Bitcoin cryptocurrency being called Altcoin.
Is Altcoin a derogatory term?
No, it is not. Some people feel Altcoin as a derogatory term for non-Bitcoin cryptocurrencies, but it is actually a neutral term.