physically weak, as from age or sickness; frail.

weak intellectually or morally

a feeble mind.

lacking in volume, loudness, brightness, distinctness, etc.

a feeble voice; feeble light.

lacking in force, strength, or effectiveness

feeble resistance; feeble arguments.

noun

ability , effectiveness , health , heartiness , power , soundness , strength

noun

debility , decrepitude , delicacy , disease , effeteness , enervation , etiolation , exhaustion , flimsiness , frailness , frailty , inability , inadequacy , incapacity , incompetence , ineffectualness , infirmity , infirmness , insignificance , insufficiency , lameness , languor , lassitude , malaise , senility , sickliness , unhealthiness , weakness , delicateness , fragileness , fragility , insubstantiality , puniness , unsoundness , unsubstantiality , weakliness