The Collaborative International Dictionary of English v.0.48:
Weak \Weak\ (w[=e]k), a. [Compar. Weaker (w[=e]k"[~e]r);
superl. Weakest.] [OE. weik, Icel. veikr; akin to Sw. vek,
Dan. veg soft, flexible, pliant, AS. w[=a]c weak, soft,
pliant, D. week, G. weich, OHG. weih; all from the verb seen
in Icel. v[imac]kja to turn, veer, recede, AS. w[imac]can to
yield, give way, G. weichen, OHG. w[imac]hhan, akin to Skr.
vij, and probably to E. week, L. vicis a change, turn, Gr.
e'i`kein to yield, give way. [root]132. Cf. Week, Wink,
v. i. Vicissitude.]
1. Wanting physical strength. Specifically:
(a) Deficient in strength of body; feeble; infirm; sickly;
debilitated; enfeebled; exhausted.
A poor, infirm, weak, and despised old man.
Weak with hunger, mad with love. --Dryden.
(b) Not able to sustain a great weight, pressure, or
strain; as, a weak timber; a weak rope.
(c) Not firmly united or adhesive; easily broken or
separated into pieces; not compact; as, a weak ship.
(d) Not stiff; pliant; frail; soft; as, the weak stalk of
(e) Not able to resist external force or onset; easily
subdued or overcome; as, a weak barrier; as, a weak
(f) Lacking force of utterance or sound; not sonorous;
low; small; feeble; faint.
A voice not soft, weak, piping, and womanish.
(g) Not thoroughly or abundantly impregnated with the
usual or required ingredients, or with stimulating and
nourishing substances; of less than the usual
strength; as, weak tea, broth, or liquor; a weak
decoction or solution; a weak dose of medicine.
(h) Lacking ability for an appropriate function or office;
as, weak eyes; a weak stomach; a weak magistrate; a
weak regiment, or army.
2. Not possessing or manifesting intellectual, logical,
moral, or political strength, vigor, etc. Specifically:
(a) Feeble of mind; wanting discernment; lacking vigor;
spiritless; as, a weak king or magistrate.
To think every thing disputable is a proof of a
weak mind and captious temper. --Beattie.
Origen was never weak enough to imagine that
there were two Gods. --Waterland.
(b) Resulting from, or indicating, lack of judgment,
discernment, or firmness; unwise; hence, foolish.
If evil thence ensue,
She first his weak indulgence will accuse.
(c) Not having full confidence or conviction; not decided
or confirmed; vacillating; wavering.
Him that is weak in the faith receive ye, but
not to doubtful disputations. --Rom. xiv. 1.
(d) Not able to withstand temptation, urgency, persuasion,
etc.; easily impressed, moved, or overcome;
accessible; vulnerable; as, weak resolutions; weak
Guard thy heart
On this weak side, where most our nature fails.
(e) Wanting in power to influence or bind; as, weak ties;
a weak sense of honor of duty.
(f) Not having power to convince; not supported by force
of reason or truth; unsustained; as, a weak argument
or case. "Convinced of his weak arguing." --Milton.
A case so weak . . . hath much persisted in.
(g) Wanting in point or vigor of expression; as, a weak
sentence; a weak style.
(h) Not prevalent or effective, or not felt to be
prevalent; not potent; feeble. "Weak prayers." --Shak.
(i) Lacking in elements of political strength; not
wielding or having authority or energy; deficient in
the resources that are essential to a ruler or nation;
as, a weak monarch; a weak government or state.
I must make fair weather yet awhile,
Till Henry be more weak, and I more strong.
(k) (Stock Exchange) Tending towards lower prices; as, a
(a) Pertaining to, or designating, a verb which forms its
preterit (imperfect) and past participle by adding to
the present the suffix -ed, -d, or the variant form
-t; as in the verbs abash, abashed; abate, abated;
deny, denied; feel, felt. See Strong, 19
(b) Pertaining to, or designating, a noun in Anglo-Saxon,
etc., the stem of which ends in -n. See Strong, 19
4. (Stock Exchange) Tending toward a lower price or lower
prices; as, wheat is weak; a weak market.
[Webster 1913 Suppl.]
5. (Card Playing) Lacking in good cards; deficient as to
number or strength; as, a hand weak in trumps.
[Webster 1913 Suppl.]
6. (Photog.) Lacking contrast; as, a weak negative.
[Webster 1913 Suppl.]
Note: Weak is often used in the formation of self-explaining
compounds; as, weak-eyed, weak-handed, weak-hearted,
weak-minded, weak-spirited, and the like.
Weak conjugation (Gram.), the conjugation of weak verbs; --
called also new conjugation, or regular conjugation,
and distinguished from the old conjugation, or
Weak declension (Anglo-Saxon Gram.), the declension of weak
nouns; also, one of the declensions of adjectives.
Weak side, the side or aspect of a person's character or
disposition by which he is most easily affected or
influenced; weakness; infirmity.
weak sore or weak ulcer (Med.), a sore covered with pale,
flabby, sluggish granulations.