Source : Webster's Revised Unabridged Dictionary (1913)

Weakly \Weak"ly\, adv.
   In a weak manner; with little strength or vigor; feebly.

Weakly \Weak"ly\, a. [Compar. {Weaklier}; superl. {Weakliest}.]
   Not strong of constitution; infirm; feeble; as, a weakly
   woman; a man of a weakly constitution.

Source : WordNet®

weakly
     adj : lacking physical strength or vitality; "a feeble old woman";
           "her body looked sapless" [syn: {decrepit}, {debile}, {feeble},
            {infirm}, {sapless}, {weak}]
     [also: {weakliest}, {weaklier}]

weakly
     adv : in a weak or feeble manner or to a minor degree; "weakly
           agreed to a compromise"; "wheezed weakly"; "he was
           weakly attracted to her" [ant: {strongly}]
     [also: {weakliest}, {weaklier}]