liberal
Liberal, most broadly, means open, unconstrained, free. Liberal theology is, thus, an approach that does not rely exclusively on tradition.
Theological historian Gary Dorrien defines liberal theology as "the idea of a Christian perspective based on reason and experience, not external authority, that reconceptualizes the meaning of Christianity in the light of modern knowledge and ethical values."
In its origins the word has an elitist aura: the word "liber" meant "free man," or "gentleman" — someone who wasn't bound to a profession. The liberal arts, then, were the pursuits in which such a free person might engage.