The Collaborative International Dictionary of English v.0.48:

Colophon \Col"o*phon\ (k[o^]l"[-o]*f[o^]n), n. [L. colophon
   finishing stroke, Gr. kolofw`n; cf. L. culmen top, collis
   hill. Cf. Holm.]
   An inscription, monogram, or cipher, containing the place and
   date of publication, printer's name, etc., formerly placed on
   the last page of a book.
   [1913 Webster]

         The colophon, or final description, fell into disuse,
         and . . . the title page had become the principal
         direct means of identifying the book.    --De Morgan.
   [1913 Webster]

         The book was uninjured from title page to colophon.
                                                  --Sir W.
                                                  Scott.
   [1913 Webster]

WordNet (r) 3.0 (2006):

colophon
    n 1: a publisher's emblem printed in a book (usually on the
         title page)