The Collaborative International Dictionary of English v.0.48:

Frontispiece \Fron"tis*piece\, n. [F. frontispice, LL.
   frontispicium beginning, front of a church, fr. L. frons
   front + spicere, specere, to look at, view: cf. It.
   frontispizio. See Front and Spy.]
   The part which first meets the eye; as:
   (a) (Arch.) The principal front of a building. [Obs. or R.]
   (b) An ornamental figure or illustration fronting the first
       page, or titlepage, of a book; formerly, the titlepage
       itself.
       [1913 Webster]

WordNet (r) 3.0 (2006):

frontispiece
    n 1: an ornamental facade
    2: front illustration facing the title page of a book