not restricted to one sect or school or party; "religious training in a nonsectarian atmosphere"; "nonsectarian colleges"; "a wide and unsectarian interest in religion"- Bertrand Russell
(chemistry) any theory in which all matter is composed of tiny discrete finite indivisible indestructible particles; "the ancient Greek philosophers Democritus and Epicurus held atomic theories of the universe"
(psychology) a theory that reduces all mental phenomena to simple elements (sensations and feelings) that form complex ideas by association