1. breakable, delicate. 2. senile, sickly, unwell, invalid. Weak, decrepit, feeble, weakly imply a lack of strength or of good health. Weak means not physically strong, because of extreme youth, old age, illness, etc.: weak after an attack of fever. Decrepit means old and broken in health to a marked degree: decrepit and barely able to walk. Feeble denotes much the same as weak, but connotes being pitiable or inferior: feeble and almost senile. Weakly suggests a long-standing sickly condition, a state of chronic bad health: A weakly child may become a strong adult. 4. ineffective. 6. unsound, ineffective, inadequate, illogical, inconclusive, unsustained, unsatisfactory, lame, vague. 7. unintelligent, simple, foolish, stupid, senseless, silly. 8. vacillating, wavering, unstable, irresolute, fluctuating, undecided, weak-kneed. 9. slender, slim, inconsiderable, flimsy, poor, trifling, trivial. 11. wanting, short, lacking.