Source : Webster's Revised Unabridged Dictionary (1913)

Responsibility \Re*spon`si*bil"i*ty\ (r?*sp?n`s?*b?l"?*t?), n.;
   pl. {-ties} (-t?z). [Cf. F. responsabilit['e].]
   1. The state of being responsible, accountable, or
      answerable, as for a trust, debt, or obligation.

   2. That for which anyone is responsible or accountable; as,
      the resonsibilities of power.

   3. Ability to answer in payment; means of paying.

Source : WordNet®

responsibility
     n 1: the social force that binds you to your obligations and the
          courses of action demanded by that force; "we must
          instill a sense of duty in our children"; "every right
          implies a responsibility; every opportunity, an
          obligation; every possession, a duty"- John
          D.Rockefeller Jr [syn: {duty}, {obligation}]
     2: the proper sphere or extent of your activities; "it was his
        province to take care of himself" [syn: {province}]
     3: a form of trustworthiness; the trait of being answerable to
        someone for something or being responsible for one's
        conduct; "he holds a position of great responsibility"
        [syn: {responsibleness}] [ant: {irresponsibility}, {irresponsibility}]