Source : Webster's Revised Unabridged Dictionary (1913)

Immunity \Im*mun"i*ty\, n.
   The state of being insusceptible to poison, the contagion of
   disease, etc.

Immunity \Im*mu"ni*ty\, n.; pl. {Immunities}. [L. immunitas, fr.
   immunis free from a public service; pref. im- not + munis
   complaisant, obliging, cf. munus service, duty: cf. F.
   immunit['e]. See {Common}, and cf. {Mean}, a.]
   1. Freedom or exemption from any charge, duty, obligation,
      office, tax, imposition, penalty, or service; a particular
      privilege; as, the immunities of the free cities of
      Germany; the immunities of the clergy.

   2. Freedom; exemption; as, immunity from error.

Source : WordNet®

immunity
     n 1: the state of not being susceptible; "unsusceptibility to
          rust" [syn: {unsusceptibility}] [ant: {susceptibility}]
     2: (medicine) the condition in which an organism can resist
        disease [syn: {resistance}]
     3: the quality of being unaffected by something; "immunity to
        criticism"
     4: an act exempting someone; "he was granted immunity from
        prosecution" [syn: {exemption}, {granting immunity}]