All the term “civil war” means is a war between citizens of the same country, as opposed to a foreign war which is between members of two or more countries. Now, you can take the South’s position that it ceased to be a part of the US once it said so, and therefore it was a foreign country. But by no means does the term imply the South was fighting for control of the US federal government. The American Revolutionary War, for instance, was a civil war in which the sides were fighting for the independence or dependence of the American colonies from the British empire.
Well, according to dictionary.com, I stand corrected!