Synonyms for Weak (same or very similar meaning)
WordNet sense 1 (being or moving lower in position or less in some value):
down
WordNet sense 2 (capable of being wounded or hurt):
vulnerable
WordNet sense 3 (inferior in strength or significance):
puny
WordNet sense 4 ((of light) lacking in intensity or brightness; dim or feeble):
pale
WordNet sense 5 (weak in willpower, courage or vitality):
spineless
WordNet sense 6 (lacking solidity or strength and liable to break):
flimsy, fragile
WordNet sense 7 (having little substance or significance):
slight, thin
WordNet sense 8 (lacking in strength or firmness or resilience):
flaccid, limp
WordNet sense 9 (pathetically lacking in force or effectiveness):
feeble, lame, lame
WordNet sense 10 (lacking strength or vigor):
faint
WordNet sense 11 (lacking strength or vigor):
enervated, debilitated, asthenic
WordNet sense 12 (used of vowels or syllables; pronounced with little or no stress):
light, unaccented
WordNet sense 13 (not bearing a stress or accent):
unstressed
WordNet sense 14 (not having or showing or requiring special skill or proficiency):
unskilled
WordNet sense 15 (lacking physical strength or vitality):
decrepit, infirm, rickety, sapless, weakly, debile
WordNet sense 16 (physically weak):
frail
WordNet sense 17 (lacking power):
powerless
WordNet sense 18 (capable of being perceived by the mind or senses):
perceptible
WordNet sense 19 (having the attributes of man as opposed to e.g. divine beings):
imperfect
WordNet sense 20 (having human form or attributes as opposed to those of animals or divine beings):
human
WordNet sense 21 (likely to fail or make errors):
fallible
WordNet sense 22 (overly diluted; thin and insipid):
washy, watery
WordNet sense 23 (reduced in strength or concentration or quality or purity):
dilute
WordNet sense 24 (lacking or marked by lack of intellectual acuity):
stupid
From the ODE community, based on WordNet
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