Source : Webster's Revised Unabridged Dictionary (1913)

Faithful \Faith"ful\, a.
   1. Full of faith, or having faith; disposed to believe,
      especially in the declarations and promises of God.

            You are not faithful, sir.            --B. Jonson.

   2. Firm in adherence to promises, oaths, contracts, treaties,
      or other engagements.

            The faithful God, which keepeth covenant and mercy
            with them that love him.              --Deut. vii.
                                                  9.

   3. True and constant in affection or allegiance to a person
      to whom one is bound by a vow, be ties of love, gratitude,
      or honor, as to a husband, a prince, a friend; firm in the
      observance of duty; loyal; of true fidelity; as, a
      faithful husband or servant.

            So spake the seraph Abdiel, faithful found, Among
            the faithless, faithful only he.      --Milton.

   4. Worthy of confidence and belief; conformable to truth ot
      fact; exact; accurate; as, a faithful narrative or
      representation.

            It is a faithful saying.              --2 Tim. ii.
                                                  11.

   {The Faithful}, the adherents of any system of religious
      belief; esp. used as an epithet of the followers of
      Mohammed.

   Syn: Trusty; honest; upright; sincere; veracious;
        trustworthy. -- {Faith"ful*ly}, adv. -{Faith"ful*ness},
        n.

Source : WordNet®

faithfulness
     n : the quality of being faithful [syn: {fidelity}] [ant: {infidelity},
          {infidelity}]