Mirabilis translates to "marvelous" or "wonderful." It's a beautiful Latin-derived word that evokes a sense of awe and wonder, fitting perfectly with the sacred theme of the song.
In "Panis Angelicus," the phrase "O res mirabilis!" (Oh, marvelous thing!) is used to express profound astonishment and reverence for the divine mystery being described. It's a word that stands out due to its classical elegance and powerful meaning.