The Collaborative International Dictionary of English v.0.48:

Memorable \Mem"o*ra*ble\, a. [L. memorabilis, fr. memorare to
   bring to remembrance, fr. memor mindful, remembering. See
   Memory, and cf. Memorabilia.]
   Worthy to be remembered; very important or remarkable. --
   Mem"o*ra*ble*ness, n. -- Mem"o*ra*bly, adv.
   [1913 Webster]

         Surviving fame to gain,
         Buy tombs, by books, by memorable deeds. --Sir J.
                                                  Davies.
   [1913 Webster]

WordNet (r) 3.0 (2006):

memorable
    adj 1: worth remembering