Source : Webster's Revised Unabridged Dictionary (1913)

Impotent \Im"po*tent\, n.
   One who is imoitent. [R.] --Shak.

Impotent \Im"po*tent\, a. [F. impotent, L. impotens, -entis;
   pref. im- not + potens potent, powerful. See {Potent}.]
   1. Not potent; wanting power, strength. or vigor. whether
      physical, intellectual, or moral; deficient in capacity;
      destitute of force; weak; feeble; infirm.

            There sat a certain man at Lystra, impotent inhis
            feet.                                 --Acts xiv. 8.

            O most lame and impotent conclusion!  --Shak.

            Not slow to hear, Nor impotent to save. --Addison.

   2. Wanting the power of self-restraint; incontrolled;
      ungovernable; violent.

            Impotent of tongue, her silence broke. --Dryden.

   3. (Med.) Wanting the power of procreation; unable to
      copulate; also, sometimes, sterile; barren.

Source : WordNet®

impotent
     adj 1: lacking power or ability; "Technology without morality is
            barbarous; morality without technology is impotent"-
            Freeman J.Dyson; "felt impotent rage" [ant: {potent}]
     2: (of a male) unable to copulate [ant: {potent}]