The Collaborative International Dictionary of English v.0.48:

Diversify \Di*ver"si*fy\, v. t. [imp. & p. p. Diversified; p.
   pr. & vb. n. Diversifying.] [F. diversifier, LL.
   diversificare, fr. L. diversus diverse + ficare (in comp.),
   akin to facere to make. See Diverse.]
   To make diverse or various in form or quality; to give
   variety to; to variegate; to distinguish by numerous
   differences or aspects.
   [1913 Webster]

         Separated and diversified on from another. --Locke.
   [1913 Webster]

         Its seven colors, that diversify all the face of
         nature.                                  --I. Taylor.
   [1913 Webster]

WordNet (r) 3.0 (2006):

diversify
    v 1: make (more) diverse; "diversify a course of study"
    2: spread into new habitats and produce variety or variegate;
       "The plants on this island diversified" [syn: diversify,
       radiate]
    3: vary in order to spread risk or to expand; "The company
       diversified" [syn: diversify, branch out, broaden]
       [ant: narrow, narrow down, specialise, specialize]