You must mean like people that use terms like "republicrat". I never even heard of it before, wikipedia says it's a term often used by liberals, which does make perfect sense.
It's used by a lot of people to show disdain for two parties that are sometimes hard to differentiate, acting much the same, giving no real reason to vote for one over the other. In my case, both now seem to be for big government, big spending, expanded federal power, illegal immigration, promotion of corporate special interests to the detriment of the people, and control over your personal life. About the only practical difference now is in national security, and that's just a recent rift in the duopoly.