The Collaborative International Dictionary of English v.0.48:
Mortal \Mor"tal\, a. [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.
5. Affecting as if with power to kill; deathly.
The nymph grew pale, and in a mortal fright.
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.