Source : Webster's Revised Unabridged Dictionary (1913)

Unlisted \Un*list"ed\, a.
   Not listed; specif. (New York Stock Exchange), admitted to
   quotation in the unlisted department, that is, admitted to be
   dealt in on the floor, but not to the ``regular list.''

Source : WordNet®

unlisted
     adj 1: not on a list; "an unlisted telephone number" [ant: {listed}]
     2: not having your name entered on a voting list; "an unlisted
        voter"