Source : Webster's Revised Unabridged Dictionary (1913)

Retentive \Re*ten"tive\, a. [Cf. F. r['e]tentif.]
   Having power to retain; as, a retentive memory.

         Nor airless dungeon, nor strong links of iron, Can be
         retentive to the strength of spirit.     --Shak.

Retentive \Re*ten"tive\, n.
   That which retains or confines; a restraint. [R.] --Bp. Hall.

Source : WordNet®

retentive
     adj : tending to retain; "a retentive memory"; "soils retentive of
           moisture" [ant: {unretentive}]