The Catholic website, which I think most would agree with states:
Original sin may be taken to mean: (1) the sin that Adam committed; (2) a consequence of this first sin, the hereditary stain with which we are born on account of our origin or descent from Adam.
From the earliest times the latter sense of the word was more common, as may be seen by St. Augustine's statement: "the deliberate sin of the first man is the cause of original sin" (De nupt. et concup., II, xxvi, 43). It is the hereditary stain that is dealt with here.
http://www.newadvent.org/cathen/11312a.htm
I can probably (maybe, almost) accept your interpretation of "absent of faith" (I'd have to think about it.) I cannot accept the author's contention that it's a fear of our own mortality. I don't see that anywhere in the definition provided by Augustine.