piercedhearts.org: “IMMACULATE CONCEPTION. These words fell from the lips of the Immaculata herself. Hence, they must tell us in the most precise and essential manner who she really is.
Since human words are incapable of expressing divine realities, it follows that these words: “Immaculate,” and “Conception” must be understood in a much more profound, much more beautiful and sublime meaning than usual: a meaning beyond that which human reason at its most penetrating, commonly gives to them.
St. Paul wrote, quoting the Prophet Isaiah: “Things that the eye has not seen, that the ear has not heard, that the heart of man has not imagined” (Is. 64,4), such are the good things that God has prepared for those who love him (I Cor. 2,9). Here, these words apply fully.
However, we can and should reverently inquire into the mystery of the Immaculata and try to express it with words provided by our intelligence using its own proper powers. Full sermon is here.