It's odd. When RINO first came into vogue, it referred to a republican who generally held to small govt ideals, but who was willing to compromise on taxes because he/she generally thought medicare and soc sec were here to stay, so we probably should pay for them.
Along the way it took some turns. If a Senator from ... say ... Miss wanted to remove an old bridge across the Big River that tied up barge traffic, and replace it with a modern one, then the only way to get that kind of money was an earmark. Earmarks were of course abused, but it came into vogue to simply not get infrastructure. I think seeign how Sandy relief did get funded has sort of put that to rest.
But, now Rino seems to include not just the old guys who'd compromise on Soc Sec, like Reagan did, but now it encompases social conservativism, as well as the notion that ANYTHING govt does is inherently evil.