Passing, n.
The act of one who, or that which, passes; the act of going by or away. Passing bell, a tolling of a bell to announce that a soul is passing, or has passed, from its body (formerly done to invoke prayers for the dying); also, a tolling during the passing of a funeral procession to the grave, or during funeral ceremonies. Sir W. Scott. Longfellow.
2 other Webster entries under this spelling
Passing, a.
1. Relating to the act of passing or going; going by, beyond, through, or away; departing.
2. Exceeding; surpassing, eminent. Chaucer. "Her passing deformity." Shak. Passing note (Mus.), a character including a passing tone. -- Passing tone (Mus.), a tone introduced between two other tones, on an unaccented portion of a measure, for the sake of smoother melody, but forming no essential part of the harmony.
Passing, adv.
Exceedingly; excessively; surpassingly; as, passing fair; passing strange. "You apprehend passing shrewdly." Shak.
Shades of meaning
Fernald has no entry of its own for passing; he lists it under transient.
He lists it without comment; the entries above explain its neighbors.