The Collaborative International Dictionary of English v.0.48:

Fidelity \Fi*del"i*ty\, n. [L. fidelitas: cf. F. fid['e]lit['e].
   See Fealty.]
   Faithfulness; adherence to right; careful and exact
   observance of duty, or discharge of obligations. Especially:
   (a) Adherence to a person or party to which one is bound;
       loyalty.
       [1913 Webster]

             Whose courageous fidelity was proof to all danger.
                                                  --Macaulay.
       [1913 Webster]

             The best security for the fidelity of men is to
             make interest coincide with duty.    --A. Hamilton.
   (b) Adherence to the marriage contract.
   (c) Adherence to truth; veracity; honesty.
       [1913 Webster]

             The principal thing required in a witness is
             fidelity.                            --Hooker.

   Syn: Faithfulness; honesty; integrity; faith; loyalty;
        fealty.
        [1913 Webster]

WordNet (r) 3.0 (2006):

fidelity
    n 1: accuracy with which an electronic system reproduces the
         sound or image of its input signal
    2: the quality of being faithful [syn: fidelity,
       faithfulness] [ant: infidelity, unfaithfulness]

The Devil's Dictionary (1881-1906):

FIDELITY, n.  A virtue peculiar to those who are about to be betrayed.