1.NounA theory or doctrine which supports a state of separation between organizations, institutions, or other societal groups (e.g. between church and state) or between different political jurisdictions (e.g. a country and its former colony).
"She wrote an essay expounding the tenets of Scottish separatism."
2.NounThe practice of treating members of different societal groups in a politically, legally, or economically different manner.
"Apartheid was a government-enforced form of separatism in which people received unequal social benefits based on race."