Mortal, a.
Etymology: [F. mortel, L. mortalis, from mors, mortis, death, fr. moriri 8die; akin to E. murder. See Murder, and cf. Filemot, Mere a lake, Mortgage.]
1. Subject to death; destined to die; as, man is mortal.
2. Destructive to life; causing or occasioning death; terminating life; exposing to or deserving death; deadly; as, a mortal wound; a mortal sin.
3. Fatally vulnerable; vital. Last of all, against himself he turns his sword, but missing the mortal place, with his poniard finishes the work. Milton.
4. Of or pertaining to the time of death. Safe in the hand of one disposing Power, Or in the natal or the mortal hour. Pope.
3 more senses
5. Affecting as if with power to kill; deathly. The nymph grew pale, and in a mortal fright. Dryden.
6. Human; belonging to man, who is mortal; as, mortal wit or knowledge; mortal power. The voice of God To mortal ear is dreadful. Milton.
7. Very painful or tedious; wearisome; as, a sermon lasting two mortal hours. [Colloq.] Sir W. Scott. Mortal foe, Mortal enemy, an inveterate, desperate, or implacable enemy; a foe bent on one's destruction.
1 other Webster entry under this spelling
Mortal, n.
A being subject to death; a human being; man. "Warn poor mortals left behind." Tickell.
Shades of meaning
Fernald lists mortal only as an antonym, under venial.
He lists it without comment; the entries above explain its neighbors.