Source : Webster's Revised Unabridged Dictionary (1913)

Weaken \Weak"en\, v. t. [imp. & p. p. {Weakened}; p. pr. & vb.
   n. {Weakening}.]
   1. To make weak; to lessen the strength of; to deprive of
      strength; to debilitate; to enfeeble; to enervate; as, to
      weaken the body or the mind; to weaken the hands of a
      magistrate; to weaken the force of an objection or an
      argument.

            Their hands shall be weakened from the work, that it
            be not done.                          --Neh. vi. 9.

   2. To reduce in quality, strength, or spirit; as, to weaken
      tea; to weaken any solution or decoction.

Source : WordNet®

weakened
     adj 1: impaired by diminution [syn: {diminished}, {lessened}, {vitiated}]
     2: made weak or weaker
     3: reduced in strength; "the faded tones of an old recording"
        [syn: {attenuate}, {attenuated}, {faded}]
     4: mixed with water; "sold cut whiskey"; "a cup of thinned
        soup" [syn: {cut}, {thinned}]
     5: used of inanimate objects or their value [syn: {hurt}]