Source : Webster's Revised Unabridged Dictionary (1913)

Incognito \In*cog"ni*to\, a. or adv. [It. incognito, masc.,
   incognita, fem., L. incognitus unknown; pref. in- not +
   cognitus known, p. p. of cognoscere: cf. F. incognito, fr.
   {It}. See {Cognition}.]
   Without being known; in disguise; in an assumed character, or
   under an assumed title; -- said esp. of great personages who
   sometimes adopt a disguise or an assumed character in order
   to avoid notice.

         'T was long ago Since gods come down incognito.
                                                  --Prior.

         The prince royal of Persia came thither incognito.
                                                  --Tatler.

Incognito \In*cog"ni*to\, n.; pl. {Incognitos}. [See
   {Incognito}, a.]
   1. One unknown or in disguise, or under an assumed character
      or name.

   2. The assumption of disguise or of a feigned character; the
      state of being in disguise or not recognized.

            His incognito was endangered.         --Sir W.
                                                  Scott.

Source : WordNet®

incognito
     adj : with your identity concealed [syn: {incognito(p)}]
     adv : without revealing one's identity; "in Holland he lived
           incognito as a carpenter in the shipyards of the East
           India company"