Source : Webster's Revised Unabridged Dictionary (1913)

Lackluster \Lack"lus`ter\, Lacklustre \Lack"lus`tre\, n.
   A want of luster. -- a. Wanting luster or brightness.
   ``Lackluster eye.'' --Shak.

Source : WordNet®

lacklustre
     adj 1: lacking brilliance or vitality; "a dull lackluster life"; "a
            lusterless performance" [syn: {lackluster}, {lusterless},
             {lustreless}]
     2: lacking luster or shine; "staring with lackluster eyes";
        "lusterless hair" [syn: {lackluster}, {lusterless}, {lustreless}]