NOUN (1)

1. a blank leaf inserted between the leaves of a book;

The Collaborative International Dictionary of English v.0.48:

Interleaf \In"ter*leaf`\, n.; pl. Interleaves. [See
   Interleave.]
   A leaf inserted between other leaves; a blank leaf inserted,
   as in a book.
   [1913 Webster]

The Free On-line Dictionary of Computing (17 December 2009):

Interleaf

   A document preparation system for Sun, VAX, Apollo and
   other workstations.

   (1994-11-09)