The Collaborative International Dictionary of English v.0.48:

Imaginative \Im*ag"i*na*tive\, a. [F. imaginatif.]
   1. Proceeding from, and characterized by, the imagination,
      generally in the highest sense of the word.
      [1913 Webster]

            In all the higher departments of imaginative art,
            nature still constitutes an important element.
                                                  --Mure.
      [1913 Webster]

   2. Given to imagining; full of images, fancies, etc.; having
      a quick imagination; conceptive; creative.
      [1913 Webster]

            Milton had a highly imaginative, Cowley a very
            fanciful mind.                        --Coleridge.
      [1913 Webster]

   3. Unreasonably suspicious; jealous. [Obs.] --Chaucer. --
      Im*ag"i*na*tive*ly, adv. -- Im*ag"i*na*tive*ness, n.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

imaginativeness \imaginativeness\ n.
   the capability of imagining; the power of imagination.

   Syn: imagination, vision.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

imaginativeness
    n 1: the formation of a mental image of something that is not
         perceived as real and is not present to the senses;
         "popular imagination created a world of demons";
         "imagination reveals what the world could be" [syn:
         imagination, imaginativeness, vision]