James Cutsinger is a professor of Theology and Religious Thought at the University of South Carolina. This is a longer interview in which he "talks around" a lot of different topics regarding the Perennial Philosophy.

I don't know that he ever gives a hard, propositional definition (the closest he probably gets is at 4:00 where he talks about a fundamental unanimity of thought of many philosophers throughout time about transcendent reality, something which is "transcendent and saving"), but this is a good introduction to the ideas that come out of the Perennial Tradition.

I think the discussion at 27:25 regarding religious relativism vs. what might be called "absolutism" is helpful and the interview also turns towards how perennialism can be understood from an orthodox Christian perspective in the second half (39:50).