weak 
(wēk)
(wēk)adj. weak·er, weak·est
1. Lacking physical strength, energy, or vigor; feeble.
2. Likely to fail under pressure, stress, or strain; lacking resistance: a weak link in a chain.
3. Lacking firmness of character or strength of will: a weak person unable to cope with adversity.
4.
a. Lacking intensity or strength; faint: weak light; a weak voice.
b. Lacking the proper strength or amount of ingredients: weak coffee.
c. Having low prices or few transactions: a weak market for oil stocks.
5.
a. Lacking the ability to function normally or fully: a weak heart.
b. Unable to digest food easily; readily nauseated: a weak stomach.
6.
a. Lacking or resulting from a lack of intelligence: a weak mind; weak reasoning.
b. Lacking aptitude or skill: a weak student; weak in math.
7. Lacking persuasiveness; unconvincing: a weak argument.
8. Lacking authority or the power to govern: a weak ruler.
9. Linguistics
a. Of, relating to, or being those verbs in Germanic languages that form a past tense and past participle by means of a dental suffix, as start, started; have, had; bring, brought.
b. Of, relating to, or being the inflection of nouns or adjectives in Germanic languages with a declensional suffix that historically contained an n.
10. Unstressed or unaccented in pronunciation or poetic meter. Used of a word or syllable.
11. Designating a verse ending in which the metrical stress falls on a word or syllable that is unstressed in normal speech, such as a preposition.
[Middle English weike, from Old Norse veikr, pliant; see weik-2 in the Appendix of Indo-European roots.]
Synonyms: weak, feeble, frail1, fragile, infirm, decrepit, debilitated
These adjectives mean lacking or showing a lack of strength. Weak is the most widely applicable: "These poor wretches ... were so weak they could hardly sit to their oars" (Daniel Defoe).
Feeble suggests pathetic or grievous physical or mental weakness or hopeless inadequacy: a feeble intellect; a feeble effort. Frail implies delicacy and inability to endure or withstand: "an aged thrush, frail, gaunt, and small" (Thomas Hardy).
What is fragile is easily broken, damaged, or destroyed: a fragile, expensive vase; a fragile state of mind after the accident. Infirm implies enfeeblement: "a poor, infirm, weak, and despis'd old man" (Shakespeare).
Decrepit describes what is weakened, worn out, or broken down by hard use or the passage of time: a decrepit building slated for demolition. Debilitated suggests a gradual impairment of energy or strength: a debilitated constitution further weakened by overwork.
These adjectives mean lacking or showing a lack of strength. Weak is the most widely applicable: "These poor wretches ... were so weak they could hardly sit to their oars" (Daniel Defoe).
Feeble suggests pathetic or grievous physical or mental weakness or hopeless inadequacy: a feeble intellect; a feeble effort. Frail implies delicacy and inability to endure or withstand: "an aged thrush, frail, gaunt, and small" (Thomas Hardy).
What is fragile is easily broken, damaged, or destroyed: a fragile, expensive vase; a fragile state of mind after the accident. Infirm implies enfeeblement: "a poor, infirm, weak, and despis'd old man" (Shakespeare).
Decrepit describes what is weakened, worn out, or broken down by hard use or the passage of time: a decrepit building slated for demolition. Debilitated suggests a gradual impairment of energy or strength: a debilitated constitution further weakened by overwork.